[0001] This invention relates to a cleaning resin composition used for cleaning the inside
of various molding machines. More particularly it relates to a cleaning resin composition
obtained by blending a neutral salt of an alkylbenzenesulfonic acid, an inorganic
filler and a water-repellent compound with a polyolefin resin.
[0002] Recent molding of thermoplastic resins has been more and more diversified and production
of more grades in smaller quantities has been intended. Further, due to appearance
of engineering plastics, color exchange or resin exchange inside molding machines
has been carried out within a broad temperature region, and the frequency of the color
exchange or resin exchange has also been increasing.
[0003] Heretofore, at the time of such color exchange or resin exchange, in order to remove
contaminants caused by the preceding resin inside the molding machine, i.e. in order
to clean the inside of the molding machine, the following processes have been employed:
a process of drawing out the contaminated screw inside the molding machine, followed
by scraping off the contaminants on the screw or the inner wall of the cylinder by
means of a brush or the like, i.e. the so-called hand sweeping, or a process of flowing
a colorless resin (hereinafter abbreviated to cleaning resin) through the inside of
the cylinder to clean the screw together with the cylinder (hereinafter referred to
as co-cleaning) without drawing out the screw.
[0004] However, such processes require a long time for completely cleaning the screw and
the inside of the cylinder, and in the case of the co-cleaning, a large quantity of
cleaning resins is used to cause a large loss in the economical aspect.
[0005] Thus, in order to solve such problems, a cleaning agent composed mainly of a hard
resin such as acrylic resins, a cleaning agent obtained by blending a nonionic surfactant
with a thermoplastic resin or a cleaning agent obtained by blending a lubricant such
as stearic acid with a thermoplastic resin have been developed.
[0006] However, in the former case, since the acrylic resins have high melt viscosity, a
high load is applied at the time of cleaning the inside of the molding machine and
also it is necessary to raise the temperature of the molding machine up to a considerably
high temperature, so that the resins are susceptible to thermal decomposition.
[0007] Further, there are drawbacks that operations are troublesome and require a considerably
long time, for example, before the cleaning agent is used, the die screen pack of
the molding machine should be removed, and further if the cleaning agent remains inside
the molding machine after completion of the cleaning, the remaining cleaning agent
mixes in the molded product of the succeeding resin so that the agent in the form
of a foreign matter deteriorates the appearance or the physical properties of the
molded product.
[0008] On the other hand, in the latter case, the cleaning agent obtained by blending stearic
acid or the like with a thermoplastic resin is insufficient in the cleaning effect
inside the molding machine, and in the case of the cleaning agent obtained by blending
a nonionic surfactant with a thermoplastic resin, if the service temperature of the
cleaning agent exceeds 250°C, vigorous evolution of decomposition gas occurs and also
a characteristic odor occurs to have a bad influence upon the operational environment,
and further the cleaning effect is insufficient.
[0009] EP-A-0234529 discloses a thermoplastic resin composition for cleaning a shaping apparatus
comprising a sodium salt of sulfonic acid, a water-repellent compound, a thermoplastic
resin and optionally an inorganic compound like silicon dioxide.
[0010] The present inventors have made extensive research in order to obtain a cleaning
resin composition by the use of which it is possible to effect color exchange inside
various molding machines by exchanging the composition for the preceding colored resin
or to clean the inside of the machines or to effect resin exchange for the preceding
resin inside the machines, in a small quantity of the composition, in a simple operation
and in a short time.
[0011] The present invention consists in a cleaning resin composition comprising a polyolefin
resin, a neutral salt of an alkylbenzenesulfonic acid, an inorganic filler and a water-repellent
compound blended with said polyolefin resin, characterized in that said inorganic
filler is talc or calcium carbonate and the proportions of said neutral salt of an
alkylbenzenesulfonic acid, said inorganic filler of talc or calcium carbonate and
said water-repellent compound are 1 to 20%, 1 to 30% and 0.5 to 10% each respectively,
by weight, based on the weight of said composition.
[0012] Examples of the polyolefin resin used in the present invention are polyethylene resins
such as high density polyethylene, linear low density polyethylene, low density polyethylene,
polypropylene resins such as crystalline propylene homopolymer, crystalline propylene-ethylene
copolymer, crystalline propylene-ethylene-butene-1 terpolymer or crystalline propylene-butene-1
copolymer each containing 70% by weight or more of propylene component, polybutene-1,
non-crystalline ethylene-propylene copolymer (EPR), non-crystalline ethylene-propylene-diene
terpolymer (EPDM) and mixtures of the foregoing. Among these, preferred resins are
high density polyethylene, linear low density polyethylene, crystalline propylene
homopolymer, crystalline propylene-ethylene copolymer, crystalline propylene-ethylene-butene-1
terpolymer and mixtures of the foregoing.
[0013] As the neutral salt of an alkylbenzenesulfonic acid used in the present invention,
the sodium salt of an alkylbenzenesulfonic acid is preferably used. This sodium salt
of an alkylbenzenesulfonic acid is an anionic surfactant and its decomposition-initiation
temperature is as high as 300°C. Examples of suitable alkyl groups for the neutral
salt of an alkyl benzenesulfonic acid include linear or branched alkyl groups of C₈
to C₂₀.
[0014] Thus, the surfactant displays a powerful effect upon cleaning of the inside molding
machines even within a high temperature region; thus a superior cleaning effect is
exhibited over from a low temperature region to a high temperature region.
[0015] The quantity of the neutral salt of an alkylbenzenesulfonic acid blended is 1 to
20% by weight, preferably 5 to 15% by weight based on the weight of the composition.
If the quantity thereof blended is less than 1% by weight, the cleaning effect is
small when the inside of molding machines is cleaned with the resulting composition,
while if it exceeds 20% by weight, notable foaming occurs when the resulting composition
is granulated.
[0016] The inorganic fillers used in the present invention are calcium carbonate or talc.
[0017] In the cleaning composition, the inorganic filler exerts a function of rubbing off
through a mechanical force dirties in the molding machine and the preceding resin
adhered thereto. The quantity thereof blended is 1 to 30% by weight, preferably 5
to 20% by weight based on the weight of the composition. If the blended quantity is
less than 1% by weight, the cleaning effect is insufficient, while if it exceeds 30%
by weight, the melt-fluidity of the resulting cleaning resin composition is reduced
and too a large load is applied onto the molding machine at the time of cleaning.
[0018] Examples of the water-repellent compound used in the present invention are synthetic
waxes such as polyethylene wax, silicones, natural waxes, metal salts of higher fatty
acids and mixtures of the foregoing. The quantity of the water-repellent compound
blended is 0.5 to 10% by weight, preferably 2 to 10% by weight. In the cleaning resin
composition of the present invention, the water-repellent compound exerts a lubricating
function. If the quantity of the water-repellent compound blended is less than 0.5%
by weight, the lubricating effect is small, while if it exceeds 10% by weight, the
lubricating properties are so strong that the mechanical force of the coexistent inorganic
filler inside the molding machine is reduced.
[0019] Phenolic antioxidants, thioic antioxidants or phosphorus antioxidants usually blended
with polyolefin resins may be added to the composition of the invention.
[0020] The composition of the present invention may be obtained by introducing a polyolefin
and definite quantities of a neutral salt of an alkylbenzenesulfonic acid, the inorganic
filler and a water-repellent compound and further at least one member of the above-mentioned
antioxidants into an agitating and mixing device such as Henschel mixer (tradename)
or super mixer and agitating and mixing these materials for one to 5 minutes. Further,
the resulting mixture may be subjected to melt-kneading and extruding at a melt-kneading
temperature of 180° to 220°C, preferably 190° to 210°C, by means of a single screw
extruder or a twin-screw extruder into pellet form.
[0021] The present invention will be described in more detail by way of Examples and Comparative
examples, but it should not be construed to be limited thereto. In addition, the proportions
therein refer to % by weight.
Examples 1 - 5 and Comparative examples 1 - 4
[0022] The respective blending components described in Table 1 mentioned later were introduced
into a Henschel mixer (tradename), followed by agitating and mixing them for 3 minutes,
melt-extruding the resulting mixture at a melt-kneading temperature of 210°C by means
of an extruder having a bore diameter of 35 mm and provided with a vent and extruding
the resulting material into pellet form to obtain a cleaning resin composition of
the present invention. Further, in Comparative examples 1 - 4, the respective blending
components described in Table 1 mentioned later were agitated and mixed and melt-kneaded
in the same manner as in Examples 1 - 5 to obtain pellets. With the cleaning resin
compositions obtained in these Examples and Comparative examples, 1) cleaning of an
injection molding machine and 2) cleaning of a blow molding machine were carried out
in a manner of the gist described below, respectively.

1) Example of cleaning of injection molding machine:
[0023] Black resin pellets of any of ABS resin, PPS resin and modified PPO resin, difficult
in color exchange, were injection-molded by means of a 35 tons injection molding machine
in 50 shots, followed by cleaning the inside of the molding machine with cleaning
resin compositions obtained in Examples 1-5 and Comparative examples 1-4, each in
100 g, by injection molding and repeating injection molding with a colorless polypropylene
resin as a cleaning resin by the injection molding machine until the resulting molded
products were not colored, to obtain the total quantity of the cleaning resin required
therefor.
[0024] Further, the black ABS resin was injection-molded under the same conditions and repeating
injection-molding with the colorless polypropylene resin as a cleaning resin without
using the above-mentioned cleaning resin compositions until the resulting molded product
was not colored, to obtain the total quantity of the cleaning resin required therefor.
These results are collectively shown in Table 2.

2) Example of cleaning of blow molding machine:
[0025] Black resin pellets of either one of ABS resin or polyethylene resin difficult in
color exchange were extruded in 10 parisons (one parison: ca. 200g) by means of a
blow molding machine having a die diameter of 21 mm and a core diameter of 19 mm,
followed by cleaning the resulting blow molding machine with the cleaning resin compositions
obtained in Examples 1-5 and Comparative example 1-4, each in 2,000 g, and then molding
the parisons with a colorless polyethylene resin as a cleaning resin until the weld
line of the resulting parisons where color exchange was most difficult was not colored
to obtain the total quantity of the cleaning resin required therefor.
[0026] Further, parisons were molded with the ABS resin under the same conditions, followed
by molding the parisons with the colorless polyethylene resin as a cleaning resin
without using the cleaning resin compositions until the weld line of the resulting
parisons was not colored, to obtain the total quantity of the cleaning resin required
therefor. These results are collectively shown in Table 3.

[0027] According to the present invention, as seen from Tables 2 and 3, when the respective
cleaning resin compositions shown in Examples 1-5 are used each in a small quantity,
it is possible to far reduce the quantities of the cleaning resin used as compared
with those shown in Comparative example 1-4. and display a notably excellent cleaning
effect.
[0028] The cleaning resin composition of the present invention has a notably excellent cleaning
effect at the time of color exchange of the preceding colored resin in various molding
machines and also at the time of cleaning for exchange of the preceding resin.
[0029] Namely, by using the cleaning resin composition of the present invention in a small
quantity or by using the composition in a small quantity together with a cleaning
resin, it is possible to far reduce the quantity of cleaning resins consumed and also
notably shorten the cleaning period of time, as compared with the case where the inside
of molding machines has so far been cleaned by exchange with cleaning resins each
color exchange.
[0030] Such effect will be illustrated by cleaning of the inside of an injection molding
machine. As seen from comparison of use of the cleaning resin composition of the present
invention with use of cleaning resins alone, it is possible to reduce the quantity
of the cleaning resins required down to about ¹/₅ - ¹/₁₀ and also to shorten the cleaning
period of time down to about ¹/₅ - ¹/₁₀.
[0031] Further, the cleaning resin composition of the present invention displays a notably
excellent effect at the time of color exchange and also at the time of resin exchange
even in the case where engineering plastics such as modified PPO resin or polyphenylene
sulfide resin as the preceding resin are molded at high temperatures.
1. Reinigungsharzzusammensetzung, umfassend in Polyolefinharz, ein Neutralsalz einer
Alkylbenzolsulfonsäure, einen anorganischen Füllstoff und eine wasserabstoßende Verbindung,
die mit dem Polyolefinharz vermischt sind, dadurch gekennzeichnet, daß der anorganische Füllstoff Talkum oder Calciumcarbonat ist, und daß die Anteile
des Neutralsalzes an Alkylbenzolsulfonsäure, des anorganischen Füllstoffes, nämlich
Talkum oder Calciumcarbonat, und der wasserabstoßenden Verbindung 1 bis 20 Gew.-%,
1 bis 30 Gew.-% bzw. 0,5 bis 10 Gew.-%, jeweils bezogen auf das Gewicht der Zusammensetzung,
beträgt.
2. Reinigungsharzzusammensetzung gemäß Anspruch 1, bei dem das Polyolefinharz Polyethylen
oder Polyoropylen ist.
3. Reinigungsharzzusammensetzung gemäß Anspruch 1, die in Form von durch Schmelzverkneten
erhaltene Pellets vorliegt.
4. Verwendung einer Reinigungsharzzusammensetzung gemäß einem der vorhergehenden Ansprüche
zum Reinigen des Inneren von Formpreßvorrichtungen.
1. Composition de résine de nettoyage comprenant une résine de polyoléfine, un sel neutre
d'un acide alkylbenzènesulfonique, une charge minérale et un composé hydrophobe mélangés
avec ladite résine de polyoléfine, caractérisée en ce que ladite charge minérale est
du talc ou du carbonate de calcium et les proportions dudit sel neutre d'un acide
alkylbenzènesulfonique, de ladite charge minérale en talc ou carbonate de calcium
et dudit composé hydrophobe sont 1 à 20 %, 1 à 30 % et 0,5 à 10 % chacune, respectivement,
en poids par rapport au poids de ladite composition.
2. Composition de résine de nettoyage selon la revendication 1, dans laquelle ladite
résine de polyoléfine est du polyéthylène ou du polypropylène.
3. Composition de résine de nettoyage selon la revendication 1, qui se présente sous
la forme de pastilles obtenues par malaxage de la masse fondue.
4. Utilisation d'une composition de résine de nettoyage selon l'une quelconque des revendications
précédentes pour effectuer le nettoyage de l'intérieur de machines de moulage.