Technical Field
[0002] The present invention relates to a multi-layered elastomer article and to a method
for its manufacturing.
Background of the invention
[0003] (Per)fluoroelastomers are known to be relatively chemically inert, thermally stable
polymers, owing primarily to the strength of the carbon-fluorine bonds present in
the molecule.
[0004] Because of their properties, the (per)fluoroelastomers are desirable in many applications
which require elastomeric materials able to provide high performances, such as withstanding
to high temperatures.
[0005] However, a great number of applications in the field of oil and gas, electronics,
automotive, and aerospace require the (per)fluoroelastomers, for example, to have
electrical and thermal conductivity or to provide a barrier to gases and liquids.
[0006] With the aim to provide (per)fluoroelastomers having the above properties, it has
been proposed in the art to adhesively bond metals to (per)fluoroelastomers.
[0007] Conventional approaches, such as for example vapour coating, sputtering or ion bombardment
processes, comprise chemically or physically roughen the metal surface, followed by
a thermal fusion or adhering with the intermediary of an adhesive layer (also called
primer) between the outmost fluoropolymer layer and the metal, which also has to possess
outstanding adhesion properties towards additional top-coat (outer) layers made from
fluoropolymers.
[0008] For example,
WO 2013/101822 (3M INNOVATIVE PROPERTIES CO.) discloses a fluoroelastomer material bearing a conductive
metal overlayer bound to said fluoroelastomer material through a thin layer of titanium.
The method for making said material comprises the steps of (a) providing a fluoroelastomer
material, optionally (d) exposure of the fluoroelastomer to oxygen plasma, (b) applying
a layer of titanium metal to the fluoroelastomer material by a vapour coating method,
(c) applying a metal overlayer to the fluoroelastomer material by a vapour coating
method, and optionally (e) electroplating the fluoroelastomer.
[0009] However, high performing polymers - including, in particular, (per)fluoroelastomers
and silicone rubbers - have low surface energy, and consequently poor adhesion with
respect to metal materials.
[0010] Thus, the high performing polymers coated with metal layers using conventional approaches
can suffer of problems such as easy peeling of the metallic coating from the substrate
and poor durability of the coating.
[0011] In the field of semi-crystalline polymers,
WO 2014/154733 (SOLVAY SPECIALTY POLYMERS S.P.A.) discloses a multilayer mirror assembly made of
ethylene-chloro-trifluoro-ethylene (ECTFE), a semi-crystalline partially fluorinated
polymer, treated by a radio-frequency plasma discharge process, and then coated with
metallic nickel by electroless plating.
[0012] However, semi-crystalline polymers, such as ECTFE, and elastomers have different
chemical-physical properties and are used in different applications. Also, semi-crystalline
polymers do not undergo to elongation and, hence, they are not affected by the problems
typically encountered when using elastomers.
[0013] In particular, defects in the metallic layer applied on the surface of the elastomer
can become particularly evident when the elastomer undergoes to elongation, resulting
in a loss of continuity in the metal layer and consequent decrease or loss of the
properties imparted by the metal coating, such as for example barrier to fluids and
thermal/electrical conductivity.
[0014] FR 2139998 (DR. ING. MAX SCHLOTTER) discloses plastics and articles made therefrom which are
metal plated by conditioning their surface by a treatment with sulfur trioxide vapor
or a sulfur trioxide containing atmosphere. In particular, Example 23 discloses the
treatment of a soft rubber plate, which is first exposed to the sulfur trioxide vapor
phase, then treated with an activating solution, a reducing solution and then chemically
nickel plated. Then, the metal layer is reinforced by electroplating with a copper
deposit. The authors concluded that "when heating the plates after copper plating
to 80°C for two hours, the adherence of the copper layer to the plate is such that
the metal layer does not separate from the rubber plate but that the rubber plate
itself becomes torn".
[0015] US 2009/0017319 A (FRAMATOME CONNECTORS INT.) discloses a process for metallizing support media made
from plastic material, particularly from high temperature plastic material such as
those for electronic industry, notably semi-crystalline polymer or liquid crystal
polymers or polybutylene terephthalate (PBT) or polyphenylene sulphide (PPS) or syndiotactic
polystyrene (SPS). However, this document is completely silent about the treatment
of elastomers or article obtained therefrom.
[0016] EP 2 626 448 discloses a process for forming a metal film comprising a step (X) of applying an
agent containing a compound (a) onto the surface of a base and a step (Y) of forming
a metal film on the surface of the compound (a) by a wet-mode plating technique, wherein
the compound (a) is a compound having either an OH group or an OH-generating group,
an azide group and a triazine ring per molecule, and the base comprises a polymer.
Summary of the invention
[0017] The Applicant faced the problem to provide an elastomer article having high adhesion
to a metallic layer, such that defects in the metallic layer are avoided or at least
minimized even after the elastomer has undergone to elongation.
[0018] Thus, in a first aspect, the present invention relates to a multi-layered article
made of an elastomeric composition [composition (C)] comprising at least one elastomer,
said article having at least one surface [surface (S)] comprising:
- nitrogen-containing groups [groups (N)] and
- at least one layer [layer (L1)] adhered to said surface (S) comprising at least one
metal compound [compound (M)] selected from the group consisting of: Cu, Ni, Pd, Co,
Zn, Ag, Au, Pt, Sn;
wherein said elastomer comprises recurring units derived from at least one (per)fluorinated
monomer,
characterized in that said nitrogen-containing groups (N) are grafted onto said surface
(S) via an atmospheric plasma process performed in the presence of a nitrogen-containing
gas, which is a mixture of N
2 and H
2..
[0019] As said above, said groups (N) are grafted onto said surface (S).
[0020] Without being bounded by any theory, the Applicant believes that at least part of
said groups (N) grafted onto said surface (S) form chemical bonds with said at least
one compound (M), thus obtaining an outstanding adhesion between said surface (S)
comprising groups (N) and said layer (L1) comprising compound (M).
[0021] The expression "chemical bonds" is intended to indicate any type of chemical bond,
such as for example covalent bond, ionic bond, dipolar (or coordinate) bond, between
at least part of groups (N) grafted on the surface of the elastomer and compound (M).
[0022] Advantageously, the article according to the present invention comprising said layer
(L1) adhered to said surface (S) provides electrical and thermal conductivity and
a barrier to gases and liquids, and can withstand extreme environmental conditions
due to chemical resistance, abrasion resistance and wear resistance, while maintaining
its typical flexibility and mechanical properties.
[0023] Then, in a second aspect, the present invention relates to a method for manufacturing
a multi-layered article, said method comprising the steps of:
- (i) providing an article made of an elastomeric composition [composition (C)] comprising
at least one elastomer, wherein said elastomer comprises recurring units derived from
at least one (per)fluorinated monomer, said article having at least one surface [surface
(S-1)];
- (ii) forming nitrogen-containing groups [groups (N)] on said at least one surface
(S-1) so as to provide an elastomer article having at least one nitrogen-containing
surface [surface (S-2)], wherein said nitrogen-containing groups (N) are grafted onto
said surface (S-2) via an atmospheric plasma process performed in the presence of
a nitrogen-containing gas, which is a mixture of N2 and H2;
- (iii) contacting said at least one surface (S-2) with a first composition [composition
(C1)] comprising at least one metallization catalyst, so as to provide an article
having at least one surface [surface (S-3)] containing groups (N) and at least one
metallization catalyst; and
- (iv) contacting said at least one surface (S-3) with a second composition [composition
(C2)] containing at least one metal compound [compound (M1)], so as to provide a multi-layered
article having at least one surface [surface (S)] comprising groups (N) and at least
one layer (L1) adhered to said surface (S) comprising at least one metal compound
(M) selected from the group consisting of: Cu, Ni, Pd, Co, Ag, Au, Pt, Sn and alloys
thereof.
[0024] Optionally, the above method comprises after step (iv), step (v) of applying a third
composition [composition (C3)] containing at least one metal compound [compound (M2)]
onto said surface (S).
Detailed description of the invention
[0025] Preferably, said multi-layered article is in the form of a film or a shaped article.
[0026] The thickness of said film is not particularly limited. For example, said film can
have a thickness of between 0.5 mm and 10 mm.
[0027] The term "elastomer" as used within the present description and in the following
claims indicates amorphous polymers or polymers having a low degree of crystallinity
(crystalline phase less than 20% by volume) and a glass transition temperature value
(T
g), measured according to ASTM D3418, below room temperature. More preferably, the
elastomer according to the present invention has a T
g below 5°C, even more preferably below 0°C.
[0028] As said in the claims, said elastomer comprises recurring units derived from at least
one at least one (per)fluorinated monomer. In a preferred embodiment, said monomers
are free of nitrogen atoms.
[0029] By the expression "at least one (per)fluorinated monomer, it is hereby intended to
denote a polymer comprising recurring units derived from one or more than one (per)fluorinated
monomers. In the rest of the text, the expression "(per)fluorinated monomers" is understood,
for the purposes of the present invention, both in the plural and the singular, that
is to say that it denote both one or more than one fluorinated monomers as defined
above. The prefix "(per)" in the expression "(per)fluorinated monomer" and in the
term "(per)fluoroelastomer" means that the monomer or the elastomer can be fully or
partially fluorinated.
[0030] Non limitative examples of suitable (per)fluorinated monomers include, notably, the
followings:
- C3-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropene (HFP);
- C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride (VDF), vinyl fluoride, 1,2-difluoroethylene
and trifluoroethylene (TrFE);
- chloro- and/or bromo- and/or iodo-C2-C6 fluoroolefins, such as chlorotrifluoroethylene (CTFE);
- CH2=CH-Rf0 wherein Rf0 is a C1-C6 (per)fluoroalkyl or a C1-C6 (per)fluorooxyalkyl having one or more ether groups;
- CH2=CFORf1, wherein Rf1 is a C1-C6 fluoro- or perfluoroalkyl group, such as CF3, C2F5, C3F7;
- CF2=CFORf2, wherein Rf2 is a C1-C6 fluoro- or perfluoroalkyl group, such as CF3, C2F5, C3F7; or a C1-C12 oxyalkyl or a C1-C12 (per)fluorooxyalkyl group comprising one or more ether groups, such as perfluoro-2-propoxypropyl;
or a group of formula -CF2ORf3 in which Rf3 is a C1-C6 fluoro- or perfluoroalkyl or a C1-C6 (per)fluorooxyalkyl group comprising one or more ether groups, such as -C2F5-O-CF3;
- CF2=CFORf4, wherein Rf4 is a C1-C12 alkyl or (per)fluoroalkyl group; a C1-C12 oxyalkyl; or a C1-C12 (per)fluorooxyalkyl; said Rf4 comprising a carboxylic or sulfonic acid group, in its acid, acid halide or salt
form;
- fluorodioxoles, such as perfluorodioxoles;
- fluorosilanes, such as CF3-C2H4-Si(Rf5)3 or Ar-Si(Rf5)3 wherein each of Rf5 is independently selected from CI, C1-C3 alkyl or C1-C3 alkoxy, and Ar is a phenyl ring optionally substituted with a C1-C6 fluoro- or perfluoroalkyl group, e.g. CF3, C2F5, C3F7 or a C1-C6 (per)fluorooxyalkyl group comprising one or more ether groups, such as -C2F5-O-CF3; and CH2=CH2-Si(Rf6)3 wherein each of Rf6 is independently selected from H, F and C1-C3 alkyl, provided that at least one of said Rf6 is F.
[0031] Preferably, said (per)fluoro-elastomer has a T
g of less than 0°C, more preferably of less than -10°C, as measured as measured according
to ASTM D-3418.
[0032] Typically, said (per)fluoro-elastomer comprises recurring units derived from the
(per)fluorinated monomers cited above.
[0033] More preferably, said (per)fluoro-elastomer comprises recurring units derived from:
- C3-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropene (HFP);
- C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride (VDF), vinyl fluoride, 1,2-difluoroethylene
and trifluoroethylene (TrFE);
- CF2=CFORf1, wherein Rf1 is a C1-C6 fluoro- or perfluoroalkyl group, such as CF3, C2F5, C3F7, or a group of formula -CFOCF2ORf2 wherein Rf2 is a C1-C6 fluoro- or perfluoroalkyl group, e.g. CF3, C2F5, C3F7;
- fluorosilanes, such as CF3-C2H4-Si(Rf3)3 wherein each of Rf3 is independently selected from CI, C1-C3 alkyl or C1-C3 alkoxy, and CH2=CH2-Si(Rf4)3 wherein each of Rf4 is selected from H, F and C1-C3 alkyl.
[0034] Optionally, said (per)fluoroelastomer further comprises recurring units derived from
at least one bis-olefin.
[0035] Non limiting examples of suitable bis-olefins are selected from those of formulae
below:
- R1R2C=CH-(CF2)j-CH=CR3R4 wherein j is an integer between 2 and 10, preferably between 4 and 8, and R1, R2, R3, R4, equal or different from each other, are -H, -F or C1-C5 alkyl or (per)fluoroalkyl group;
- A2C=CB-O-E-O-CB=CA2, wherein each of A, equal or different from each other, is independently selected
from -F, -CI, and -H; each of B, equal or different from each other is independently
selected from -F, -CI, -H and - ORB, wherein RB is a branched or straight chain alkyl radical which can be partially, substantially
or completely fluorinated or chlorinated; E is a divalent group having 2 to 10 carbon
atoms, optionally fluorinated, which may be inserted with ether linkages; preferably
E is a -(CF2)z- group, with z being an integer from 3 to 5; and - R6R7C=CR5-E-O-CB=CA2, wherein E, A and B have the same meaning as above defined; R5, R6, R7, equal or different from each other, are -H, -F or C1-C5 alkyl or fluoroalkyl group.
[0036] When a bis-olefin is employed, the resulting (per)fluoroelastomer typically comprises
from 0.01% to 5% by moles of units deriving from the bis-olefin with respect to the
total amount of units in the polymer.
[0037] Optionally, said (per)fluoroelastomer may comprise cure sites, either as pendant
groups bonded to certain recurring units or as ends groups of the polymer chain, said
cure sites comprising at least one iodine or bromine atom, more preferably at least
one iodine atom.
[0038] Among cure-site containing recurring units, mention can be notably made of:
(CSM-1) iodine or bromine containing monomers of formula:

wherein each of AHf, equal to or different from each other and at each occurrence, is independently selected
from F, CI, and H; BHf is any of F, Cl, H and ORHfB, wherein RHfB is a branched or straight chain alkyl radical which can be partially, substantially
or completely fluorinated or chlorinated; each of WHf equal to or different from each other and at each occurrence, is independently a
covalent bond or an oxygen atom; EHf is a divalent group having 2 to 10 carbon atom, optionally fluorinated; RHf is a branched or straight chain alkyl radical, which can be partially, substantially
or completely fluorinated; and RHf is a halogen atom selected from the group consisting of Iodine and Bromine; which
may be inserted with ether linkages; preferably E is a -(CF2)m- group, with m being an integer from 3 to 5;
(CSM-2) ethylenically unsaturated compounds comprising cyanide groups, possibly fluorinated.
[0039] Among cure-site containing monomers of type (CSM1), preferred monomers are those
selected from the group consisting of:
(CSM1-A) iodine-containing perfluorovinylethers of formula:

with m being an integer from 0 to 5 and n being an integer from 0 to 3, with the provisio
that at least one of m and n is different from 0, and Rfi being F or CF3; (as notably described in patents US 4745165 (AUSIMONT SPA), US 4564662 (MINNESOTA MINING) and EP 199138 (DAIKIN IND LTD) ; and
(CSM-1B) iodine-containing ethylenically unsaturated compounds of formula:
CX1X2=CX3-(CF2CF2)p-I
wherein each of X1, X2 and X3, equal to or different from each other, are independently H or F; and p is an integer
from 1 to 5; among these compounds, mention can be made of CH2=CHCF2CF2I, I(CF2CF2)2CH=CH2, ICF2CF2CF=CH2, I(CF2CF2)2CF=CH2;
(CSM-1C) iodine-containing ethylenically unsaturated compounds of formula:
CHR=CH-Z-CH2CHR-I
wherein R is H or CH3, Z is a C1-C18 (per)fluoroalkylene radical, linear or branched, optionally containing one or more
ether oxygen atoms, or a (per)fluoropolyoxyalkylene radical; among these compounds,
mention can be made of CH2=CH-(CF2)4CH2CH2I, CH2=CH-(CF2)6CH2CH2I, CH2=CH-(CF2)8CH2CH2I, CH2=CH-(CF2)2CH2CH2I;
(CSM-1D) bromo and/or iodo alpha-olefins containing from 2 to 10 carbon atoms such
as bromotrifluoroethylene or bromotetrafluorobutene described, for example, in US 4035565 (DU PONT) or other compounds bromo and/or iodo alpha-olefins disclosed in US 4694045 (DU PONT).
[0040] Among cure-site containing monomers of type (CSM2), preferred monomers are those
selected from the group consisting of:
(CSM2-A) perfluorovinyl ethers containing cyanide groups of formula CF2=CF-(OCF2CFXCN)m-O-(CF2)n-CN, with XCN being F or CF3, m being 0, 1, 2, 3 or 4; n being an integer from 1 to 12;
(CSM2-B) perfluorovinyl ethers containing cyanide groups of formula CF2=CF-(OCF2CFXCN)m'-O-CF2-CF(CF3)-CN, with XCN being F or CF3, m' being 0, 1, 2, 3 or 4.
[0041] Specific examples of cure-site containing monomers of type CSM2-A and CSM2-B suitable
to the purposes of the present invention are notably those described in patents
US 4281092 (DU PONT),
US 5447993 (DU PONT) and
US 5789489 (DU PONT).
[0042] Preferably, said (per)fluoroelastomer comprises iodine or bromine cure sites in an
amount of 0.001 to 10% wt. Among these, iodine cure sites are those selected for maximizing
curing rate, so that (per)fluoroelastomers comprising iodine cure-sites are preferred.
[0043] According to this embodiment, for ensuring acceptable reactivity it is generally
understood that the content of iodine and/or bromine in the (per)fluoroelastomer should
be of at least 0.05 % wt, preferably of at least 0.1 % weight, more preferably of
at least 0.15 % weight, with respect to the total weight of the (per)fluoroelastomer.
[0044] On the other side, amounts of iodine and/or bromine not exceeding preferably 7 %
wt, more specifically not exceeding 5 % wt, or even not exceeding 4 % wt, with respect
to the total weight of the (per)fluoroelastomer, are those generally selected for
avoiding side reactions and/or detrimental effects on thermal stability.
[0045] These iodine or bromine cure sites of these preferred embodiments of the invention
might be comprised as pending groups bound to the backbone of the (per)fluoroelastomer
polymer chain (by means of incorporation in the (per)fluoroelastomer chain of recurring
units derived from monomers of (CSM-1) type, as above described, and preferably of
monomers of (CSM-1A) to (CSM1-D), as above detailed) or might be comprised as terminal
groups of said polymer chain.
[0046] According to a first embodiment, the iodine and/or bromine cure sites are comprised
as pending groups bound to the backbone of the (per)fluoroelastomer polymer chain.
The (per)fluoroelastomer according to this embodiment generally comprises recurring
units derived from iodine or bromine containing monomers (CSM-1) in amounts of 0.05
to 5 mol per 100 mol of all other recurring units of the (per)fluoroelastomer, so
as to advantageously ensure above mentioned iodine and/or bromine weight content.
[0047] According to a second preferred embodiment, the iodine and/or bromine cure sites
are comprised as terminal groups of the (per)fluoroelastomer polymer chain; the fluoroelastomer
according to this embodiment is generally obtained by addition to the polymerization
medium during fluoroelastomer manufacture of anyone of:
- iodinated and/or brominated chain-transfer agent(s); suitable chain-chain transfer
agents are typically those of formula Rf(I)x(Br)y, in which Rf is a (per)fluoroalkyl or a (per)fluorochloroalkyl containing from 1 to 8 carbon atoms,
while x and y are integers between 0 and 2, with 1 ≤ x+y ≤ 2 (see, for example, patents
US 4243770 (DAIKIN IND LTD) and US 4943622 (NIPPON MEKTRON KK) ; and
- alkali metal or alkaline-earth metal iodides and/or bromides, such as described notably
in patent US 5173553 (AUSIMONT SRL).
[0048] Among specific compositions of said (per)fluoroelastomer, which are suitable for
the purpose of the present invention, mention can be made of fluoroelastomers having
the following compositions (in mol %):
- (i) vinylidene fluoride (VDF) 35-85 %, hexafluoropropene (HFP) 10-45 %, tetrafluoroethylene
(TFE) 0-30 %, perfluoroalkyl vinyl ethers (PAVE) 0-15 %, bis-olefin (OF) 0-5 %;
- (ii) vinylidene fluoride (VDF) 50-80 %, perfluoroalkyl vinyl ethers (PAVE) 5-50 %,
tetrafluoroethylene (TFE) 0-20 %, bis-olefin (OF) 0-5 %;
- (iii) vinylidene fluoride (VDF) 20-30 %, C2-C8 non-fluorinated olefins (OI) 10-30 %, hexafluoropropene (HFP) and/or perfluoroalkyl
vinyl ethers (PAVE) 18-27 %, tetrafluoroethylene (TFE) 10-30 %, bis-olefin (OF) 0-5
%;
- (iv) tetrafluoroethylene (TFE) 50-80 %, perfluoroalkyl vinyl ethers (PAVE) 20-50 %,
bis-olefin (OF) 0-5 %;
- (v) tetrafluoroethylene (TFE) 45-65 %, C2-C8 non-fluorinated olefins (OI) 20-55 %, vinylidene fluoride 0-30 %, bis-olefin (OF)
0-5 %;
- (vi) tetrafluoroethylene (TFE) 32-60 % mol %, C2-C8 non-fluorinated olefins (OI) 10-40 %, perfluoroalkyl vinyl ethers (PAVE) 20-40 %,
fluorovinyl ethers (MOVE) 0-30 %, bis-olefin (OF) 0-5 %;
- (vii) tetrafluoroethylene (TFE) 33-75 %, perfluoroalkyl vinyl ethers (PAVE) 15-45
%, vinylidene fluoride (VDF) 5-30 %, hexafluoropropene HFP 0-30 %, bis-olefin (OF)
0-5 %;
- (viii) vinylidene fluoride (VDF) 35-85 %, fluorovinyl ethers (MOVE) 5-40 %, perfluoroalkyl
vinyl ethers (PAVE) 0-30 %, tetrafluoroethylene (TFE) 0-40 %, hexafluoropropene (HFP)
0-30 %, bis-olefin (OF) 0-5 %;
- (ix) tetrafluoroethylene (TFE) 20-70 %, fluorovinyl ethers (MOVE) 30-80 %, perfluoroalkyl
vinyl ethers (PAVE) 0-50 %, bis-olefin (OF) 0-5 %.
[0049] Suitable examples of (per)fluoroelastomers are the products sold by SOLVAY SPECIALTY
POLYMERS S.p.A. under the trade name Tecnoflon®, such as for example Tecnoflon® PL
855.
[0050] As an alternative, not within the scope of the present invention, said elastomer
can be a silicone elastomer. Preferably, said silicone elastomer has a T
g of less than -10°C, more preferably of less than -30°C, and even more preferably
of less than -50°C as measured as measured according to ASTM D-3418.
[0051] Typically, said silicone elastomer comprises recurring units derived from silicon-containing
monomers, and optionally further hydrogenated monomers and/or (per)fluorinated monomers
as disclosed above.
[0052] By the expression "silicon-containing monomer", it is hereby intended to denote a
linear or branched monomer containing alternating silicon and oxygen atoms.
[0053] Examples of suitable silicon-containing monomers include:
- silane, such as CH2=CH2-Si(Rf7)3 wherein each of Rf7 is independently selected from H, F and C1-C3 alkyl;
- siloxane of formula (R)3Si-O-Si(R)3 and (R)2Si(OH)2, wherein each R is independently selected from H, linear or branched alkyl groups
having from 1 to 6 carbon atoms, preferably methyl group, or phenyl group.
[0054] Typically, said silicone elastomer is a polyorganosiloxane-based silicone rubber
base, such as a polydimethyl siloxane containing crosslinking groups having hydroxyl,
vinyl or hexenyl groups, or a polymethylphenyl siloxane.
[0055] Suitable examples of silicone elastomers are the products sold by Dow Corning Corp.
(U.S.A.) under the trade name Silastic, such as Silastic 35U and Silastic TR-55 (dimethyl
vinyl terminated, dimethyl organosiloxane).
[0056] Said nitrogen-containing groups (N) are not particularly limited, provided that it
contains at least one nitrogen atom. Examples said of groups (N) are amino, amide,
imino, nitrile, urethane and urea groups.
[0057] The thickness of said layer (L1) is not particularly limited. For example, said layer
(L1) has a thickness of from 1 nm to 10 µm.
[0058] Preferably, said layer (L1) is a continuous layer, completely covering said surface
(S). However, depending on the application, said layer (L1) can be a discontinuous
layer, partially covering said surface (S), i.e. said surface (S) comprises at least
one area that is not covered by said layer (L1).
[0059] Examples of said compound (M) are the following comprises at least one metal selected
from the group consisting of: Rh, Ir, Ru, Ti, Re, Os, Cd, TI, Pb, Bi, In, Sb, Al,
Ti, Cu, Ni, Pd, V, Fe, Cr, Mn, Co, Zn, Mo, W, Ag, Au, Pt, Ir, Ru, Pd, Sn, Ge, Ga and
alloys thereof.
[0060] According to the invention, said compound (M) comprises at least one metal selected
from the group consisting of Ni, Cu, Pd, Co, Ag, Au, Pt, Sn and alloys thereof. Even
more preferably, said compound (M) comprises Cu and Pd.
[0061] Under step (i) of the process of the present invention, said elastomeric composition
(C) typically comprises at least one elastomer, for example in the form of slabs,
powder, crumbs, liquids, gels; and further ingredients.
[0062] Suitable further ingredients and their amounts can be selected by the skilled person,
depending on the type of elastomer used, the conditions used in the cross-linking
step and/or the properties desired in the final article.
[0063] Typically, further ingredients can be selected from the following:
- curing agents, such as polyhydroxylic compounds (for example Bisphenol A), triallyl-isocyanurate
(TAIC) and organic peroxide (for example di-tertbutyl peroxide, 2,4-dichloro benzoyl
peroxide, dibenzoyl peroxide, bis(1,1-diethylpropyl)peroxide, bis(1- ethyl-1-methylpropyl)peroxide,
1,1-diethylpropyl-1-ethyl-1-methylpropyl- peroxide, 2,5-dimethyl-2,5-bis(tert-amylperoxy)hexane,
dicumyl peroxide, di-tert-butyl perbenzoate, bis[1,3-dimethyl-3-(tert-butylperoxy)butyl]
carbonate and 2,5-bis(tert-butylper- oxy)-2,5-dimethylhexane, which is sold under
the trade name Luperox® 101XL45);
- metal compounds, in particular bivalent metal oxides and/or hydroxide, such as MgO,
ZnO and Ca(OH)2; salts of a weak acid, such as Ba, Na, K, Pb, Ca stearate, benzoates, carbonates,
oxalates, or phopshites; and mixtures thereof; and
- conventional additives, in particular fillers, such as carbon black and fumed silica;
accelerators, such as ammonium, phosphonium and aminophosphonium salt; thickeners;
pigments; antioxideant; stabilizers; processing aids.
[0064] Preferably, in composition (C), said curing agents are in an amount of from 0.5 to
15 phr (i.e., parts by weight per 100 parts by weight of the elastomer), more preferably
of from 2 to 10 phr.
[0065] Preferably, in composition (C), said metal compounds are in an amount of from 0.5
to 15 phr, more preferably of from 1 to 10 phr.
[0066] Preferably, in composition (C), said conventional additives are in an amount of from
0.5 to 50 phr, more preferably of from 3 to 40 phr.
[0067] Said composition (C) is typically manufactured by using standard methods.
[0068] Typically, all the ingredients are first mixed together. Mixer devices such as internal
mixers or open mill mixers can be used.
[0069] Under step (i) of the process of the present invention, said article is obtained
by curing said composition (C).
[0070] The conditions for the curing of said composition (C) can be selected by the skilled
person depending on the elastomer and the curing agent used.
[0071] For example, when the elastomer is a fluoroelastomer, curing can be performed at
a temperature of from 100°C to 250°C, preferably from 150° C to 200°C, for a time
of from 5 to 30 minutes.
[0072] In the method according to the present invention, said step (ii) is performed by
treating said surface (S-1) in the presence of a nitrogen-containing gas.
[0073] Said nitrogen-containing gas can be for example N
2, NH
3 or mixtures thereof, optionally in admixture with nitrogen-free gas such as CO
2 and/or H
2. Under step (ii) of the present invention, said nitrogen-containing gas is a mixture
of N
2 and H
2.
[0074] The gas rate can be selected by the skilled person. Good results have been obtained
by using gas flow between 5 nl/min and 15 nl/min, preferably of about 10 nl/min.
[0075] According to the invention, said step (ii) is performed by an atmospheric plasma
process.
[0076] Preferably, said atmospheric plasma process is performed under atmospheric pressure
and with an equivalent corona dose of from 50 Wmin/m
2 to 30,000 Wmin/m
2, more preferably of from 500 Wmin/m
2 to 15000 Wmin/m
2.
[0077] Advantageously, said at least one surface (S-1) is continuously treated by said atmospheric
plasma process in the presence of a nitrogen-containing gas, so as to provide a nitrogen-containing
surface (S-2).
[0078] The Applicant has found that the so-treated surface (S-2) provides outstanding adhesion
with a layer (L1) comprising at least one metal compound, applied thereto as disclosed
below.
[0079] Preferably, under step (iii) of the present invention, said composition (C1) is in
a solution or a colloidal suspension of the metallization catalyst in a suitable solvent,
such as water.
[0080] Preferably, step (iii) is performed by dipping the elastomer as obtained in step
(ii) in said composition (C1).
[0081] Preferably, compounds that may be employed as metallization catalysts in the method
of the present invention are selected in the group comprising Pd, Pt, Rh, Ir, Ni,
Cu, Ag and Au catalysts.
[0082] More preferably, the metallization catalyst is selected from Pd catalysts, such as
PdCl
2.
[0083] Preferably, under step (iv), said composition (C2) is an electroless metallization
plating bath, comprising at least one compound (M1), at least one reducing agent,
at least one liquid medium and, optionally, one or more additives.
[0084] Preferably, said compound (M1) comprises one or more metal salts. More preferably,
said compound (M1) preferably comprises one or more metal salts of the metals listed
above with respect to compound (M).
[0085] Preferably, said reducing agent is selected from the group comprising formaldehyde,
sodium hypophosphite, hydrazine, glycolic acid and glyoxylic acid.
[0086] Preferably, said liquid medium is selected from the group comprising water, organic
solvents and ionic liquids.
[0087] Among organic solvents, alcohols are preferred such as ethanol.
[0088] Non-limitative examples of suitable ionic liquids include, notably, those comprising
as cation a sulfonium ion or an imidazolium, pyridinium, pyrrolidinium or piperidinium
ring, said ring being optionally substituted on the nitrogen atom, in particular by
one or more alkyl groups with 1 to 8 carbon atoms, and on the carbon atoms, in particular
by one or more alkyl groups with 1 to 30 carbon atoms.
[0089] Preferably, the ionic liquid is advantageously selected from those comprising as
anion those chosen from halides anions, perfluorinated anions and borates.
[0090] Preferably, additives are selected from the group comprising salts, buffers and other
materials suitable for enhancing stability of the catalyst in the liquid composition.
[0091] Preferably, said step (iv) is performed at a temperature above 30°C, for example
between 40°C and 50°C.
[0092] Preferably, said step (iv) is performed so as to provide a continuous layer (L1),
which completely covers said surface (S), for example by dipping the elastomer as
obtained in step (iii) in said composition (C2). However, depending on the application
of the multi-layered article, said step (iv) may be performed so as to provide a discontinuous
layer (L1), which partially covers said surface (S).
[0093] Preferably, said steps (iii) and (iv) are performed as a single step [step (iii-D)],
more preferably by electroless deposition.
[0094] By "electroless deposition" it is meant a redox process typically carried out in
a plating bath between a metal cation and a proper chemical reducing agent suitable
for reducing said metal cation in its elemental state.
[0095] The preferred conditions disclosed above with respect to step (iii) and step (iv)
apply whether steps (iii) and (iv) are performed separately or when step (iii) and
step (iv) are performed as a single step (iii-D).
[0096] Preferably, said composition (C3) is an electrolytic solution, comprising at least
one compound (M2), at least one metal halide and, optionally, at least one ionic liquid
as defined above.
[0097] Said compound (M2) can be the same or different from said compound (M1).
[0098] Preferably, said compound (M2) is a metal salt deriving from Al, Ni, Cu, Ag, Au,
Cr, Co, Sn, Ir, Pt and alloys thereof.
[0099] Preferably, said metal halide is PdCl
2.
[0100] Preferably, said step (v) is performed by electro-deposition.
[0101] Within the present description and in the following claims, by "electro-deposition"
it is meant a process using electrical current to reduce metal cations from an electrolytic
solution.
[0102] The present invention will be now described in more detail with reference to the
following examples, whose purpose if merely illustrative and not limitative of the
scope of the invention.
Examples
Materials
[0103] Tecnoflon® PL855 fluoroelastomer: TFE/PMVE/MOVE terpolymer having Mooney viscosity
of about 54 and Tg of about -30°C, supplied by Solvay Specialty Polymers Italy S.p.A.
[0104] Luperox® 101XL45: 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, blend with calcium
carbonate and silica, with 45 wt.% of solid content TAIC: triallyl isocyanurate, with
75 wt.% of solid content
[0105] Commercial copper electroless solution Printoganth PV, supplied by Atotech
Example 1 - Production of an elastomer article [Plaque 1C]
[0106] The ingredients listed in the following Table 1 were mixed together in an open mill
mixer.
Table 1
| Ingredients |
Amount (phr) |
| Tecnoflon® PL855 |
100 |
| Carbon Black N990 |
30 |
| ZnO |
5 |
| Luperox® 101XL45 |
3 |
| TAIC |
4 |
[0107] The composition thus obtained was press-cured for 10 minutes at 170°C, so as to form
plaques of 2 mm thick and 130 mm of side. The plaques were then post-cured in an oven
(in air) for 24 hours at 250°C.
[0108] The plaques thus obtained were then cleaned with a lab cloth soaked with isopropyl
alcohol (IPA), in order to remove dirt and contaminants.
[0109] One of the plaque thus obtained was used as reference plaque (hereinafter referred
to as "
Plaque 1C")
.
Example 2 - Manufacture of a multi-layered elastomer article
[0110] One of the plaques obtained according to the procedure described in Example 1 was
treated as follows.
Step (a) [Plaque AP]
[0111] An atmospheric plasma treatment was performed on one surface of the plaque by means
of a Dielectric Barrier Discharge (DBD) device with mobile upper electrode, in the
following conditions:
electrode distance 3mm
gas flow 10 nl/min
gas composition 95% N2 + 5% H2
source power 400W
mobile electrode speed 2m/min and 3 passes
[0112] The treatment resulted in an equivalent corona dose of about 8700 W min/m
2.
[0113] The plaque thus obtained will be hereinafter referred to as "
Plaque AP"
.
Step (b) [Plaque 2]
[0114] Plaque AP obtained according to the procedure disclosed in step (a) was subjected
to electroless deposition in order to obtain a layer of metallic copper.
[0115] The plaque was cleaned by dipping in a suitable solution containing isopropyl alcohol
and, then, contacted with a PdCl
2 solution.
[0116] The palladium ions were reduced to metallic palladium. Then, electroless deposition
of copper was performed by dipping the sample in the bath containing the Atotech's
Printogant PV solution, for 90 seconds, at 45°C, so as the metallic copper was deposited
on the surface of the plaque.
[0117] The plaque thus obtained will be hereinafter referred to as "
Plaque 2"
.
Comparative Example 3 - Manufacture of a comparative multi-layered elastomer article
[Plaque 3C]
[0118] One plaque obtained according to the procedure described in Example 1 above was treated
according to the procedure described in Example 2, step (b), without performing the
atmospheric plasma treatment.
[0119] The plaque thus obtained will be hereinafter referred to as "
Plaque 3C"
.
Comparative Example 4 - Manufacture of a comparative multi-layered elastomer article
[Plaque 4C]
[0120] One plaque obtained according to the procedure described in Example 1 above was deposited
with a copper layer by sputtering technique, i.e. in particular by eroding copper
atoms from a copper electrode using an argon plasma and depositing said copper onto
the plaque.
[0121] The plaque thus obtained will be hereinafter referred to as "
Plaque 4C"
.
Example 5 - Surface analysis
5a - Surface analysis by ATR-FTIR
[0122] Attenuated total reflection (ATR) is a sampling technique used in conjunction with
infrared (IR) spectroscopy which enables samples to be examined directly in the solid
or liquid state. Fourier transform infrared (FTIR) spectroscopy is a measurement technique
that allows to record IR spectra.
[0123] The surface of Plaque AP obtained after step (a) of Example 2 was analysed by ATR-FTIR,
as follows.
[0124] A piece measuring 20mm x 30mm of the treated plaque was subjected to measurements
performed with Ge crystal, with a resolution of 2cm
-1 and 256 scans.
[0125] The same analysis was performed on the surface of Plaque 1C, obtained following the
procedure disclosed in Example 1 and having the same measures of Plaque AP.
[0126] The results were compared by performing spectral subtraction between the spectra
obtained for Plaque AP and Plaque 1C, and weak positive bands were observed in the
region at about 3300 cm
-1 and from 1680 cm
-1 to 1500 cm
-1, which were compatible with the presence of chemical groups containing nitrogen atoms
like amide, urethanes and ureas.
[0127] The comparison of the peaks in the functional region of ATR-FTIR spectra is showed
in Table 2.
Table 2
| Plaque |
Positive peak at 3300 cm-1 |
Positive peaks between 1680 cm-1 and 1500 cm-1 |
| 1C(*) |
- |
- |
| AP |
Compatible with N containing groups |
Compatible with N containing groups |
[0128] The above results showed that atmospheric plasma treatment modified the surface of
the elastomer plaque, by introducing nitrogen-containing groups.
Example 5b - Surface analysis by X-Ray (XPS)
[0129] X-ray Photoelectron Spectroscopy (XPS) is a surface analysis, which provides quantitative
and chemical state information from the surface of the material being studied. The
average depth of analysis was approximately 5 nm, so that it was possible to obtain
the actual composition of the sample surface.
[0130] The surface of Plaque 2 obtained after step (b) of Example 2 was analysed by XPS.
[0131] The same analysis was performed on the surface of Plaque 1C, obtained following the
procedure disclosed in Example 1.
[0132] The comparison between Nitrogen, Palladium and Copper concentration observed on Plaque
1C and Plaque 2 is showed in Table 3.
Table 3
| Plaque |
Atomic concentration (%) |
| N |
Pd |
Cu |
| 1C(*) |
0% |
0% |
0% |
| 2 |
1.32% |
0.46% |
4.77% |
[0133] The above results showed that Plaque 2, which is an examples of the multilayer article
according to the present invention, contains the nitrogen-containing groups, as well
as palladium and copper atoms.
Example 6 - Evaluation of adhesion of the metallic layer
[0134] The adhesion of the metallic layer was evaluated on the following plaques:
- Plaque 2 obtained according to the procedure described in Example 2,
- Plaque 3C obtained according to the procedure described in Comparative Example 3 and
- Plaque 4C obtained according to the procedure described in Comparative Example 4.
[0135] The adhesion was evaluated as follows: using a cutting tool, two series of perpendicular
cuts were performed on the metallic layer of Plaque 2, Plaque 3C and Plaque 4C, in
order to create a lattice pattern on them. A piece of tape was then applied and smoothened
over the lattice and removed with an angle of 180° with respect to the metallic layer.
[0136] The adhesion of metallic layer was then assessed for Plaque 2, Plaque 3C and Plaque
4C by comparing the lattice of cuts with the ASTM D3359 standard procedure. The classification
of test results ranged from 5B to 0B, whose descriptions are depicted in Table 4 herein
below.
Table 4
| ASTM D3359 Classification |
Description |
| 5B |
The edges of the cuts are completely smooth; none of the squares of the lattice is
detached. |
| 4B |
Detachment of flakes of the coating at the intersections of the cuts. A cross cut
area not significantly greater than 5% is affected. |
| 3B |
The coating has flaked along the edges and/or at the intersection of the cuts. A cross
cut area significantly greater than 5%, but not significantly greater than 15% is
affected. |
| 2B |
The coating has flaked along the edges of the cuts partly or wholly in large ribbons,
and/or it has flaked partly of wholly on different parts of the squares. A cross cut
area significantly greater than 15%, but not significantly greater than 65%, is affected. |
| 1B |
The coating has flaked along the edges of the cuts in large ribbons and/or some squares
have |
| |
detached partly or wholly. A cross cut area significantly greater than 35%, but not
significantly greater than 65%, is affected. |
| 0B |
Any degree of flaking that cannot be classified even by classification 1B. |
[0137] The adhesion value obtained for the plaques was as follows:
- Plaque 2 = 5B;
- Plaque 3C = 1B;
- Plaque 4C = 1B
[0138] The above results demonstrated the excellent adhesion achieved in the elastomer article
according to the present invention.
Example 7 - Evaluation of mechanical properties
[0139] The mechanical properties of Plaque 2 obtained according to the procedure described
in Example 2 and Plaque 1C obtained according to the procedure described in Example
1 were evaluated with tensile tests following the DIN 53504 S2 standard procedure.
[0140] The measured mechanical properties are showed in Table 5.
Table 5
| |
Plaque 1C(*) |
Plaque 2 |
| Stress at 20% of strain [MPa] |
4.6 |
4.9 |
| Stress at 50% of strain [MPa] |
7.7 |
8.0 |
| Stress at 100% of strain [MPa] |
14.7 |
14.9 |
| Stress at break [MPa] |
20.5 |
22.1 |
| Strain at break [%] |
137 |
140 |
[0141] By visual assessment made during and after the test, it was verified that the metal
layer remained completely adherent to the surface of Plaque 2 and that it followed
the elongation of the same.
[0142] The above results demonstrated that the mechanical properties of Plaque 1C(*) comprising
the pristine elastomer were not altered by the procedure described in Example 2 and
that an excellent adhesion was achieved in multi-layered elastomer article according
to the present invention.