JPH041011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a process for producing substantially anti-caking, low tack rubber pellets.

Olefin copolymer rubbers, such as ethylene-propylene copolymer rubber and ethylene-propylene-polyene copolymer rubber, are usually supplied on the market in the form of blocks, such as pales.

However, such block-shaped olefin copolymer rubber has drawbacks such as the trouble of taking it out from storage, the trouble of supplying it to the equipment used in the molding process, the trouble of transporting it, and the difficulty in measuring it. It was hot. Therefore, if olefin copolymer rubber could be provided on the market in the form of pellets, the above-mentioned drawbacks would be overcome, and furthermore, the olefin copolymer rubber would be free from fillers, softeners, vulcanizing agents, etc. that are commonly used with olefin copolymer rubber. To supply pellet-shaped olefin copolymer rubber and compounding agents directly to an extruder with high production efficiency, instead of mixers with poor production efficiency such as the Banbury mixer conventionally used when kneading the compounding agents. This brings about great advantages such as making it possible to prepare compounded rubber.

However, even when rubbers such as olefin copolymer rubbers are formed into pellets, the copolymer rubber itself is sticky, so that it condenses into blocks during storage, and the purpose of forming it into pellets is lost.

Various methods have been proposed to reduce the stickiness of the surface of such sticky pellets. For example, a method is known in which pellets that tend to become sticky are coated with inorganic powder such as talc, silica, calcium carbonate, or polyethylene powder as an anti-sticking agent, thereby adhering these powders to pellets that tend to become sticky. However, since inorganic materials such as talc and silica are not compatible with rubber, adhesion of these powders often has an adverse effect on performance in end uses. In addition, in this method, in order to substantially prevent the pellets from coagulating, it is necessary to mix the anti-blocking agent powder with the pellets in an amount of several percent to more than 10 percent, and if such an amount of powder is mixed, the properties of the rubber being treated will be impaired. There are some drawbacks. For example, when polyethylene powder is sprinkled on olefin copolymer rubber pellets,
If the amount of powder deposited increases, there is a drawback that the rubbery properties of the olefin copolymer rubber vulcanizate deteriorate.

As an excellent anti-stick method for rubber pellets that does not have these drawbacks, a technique based on the discovery that coating rubber pellets with higher fatty acids or their salts prevents stickiness and does not substantially impair the properties of rubber was disclosed in JP-A-56- 136347, but it still has the following drawbacks.

In other words, in the method disclosed in the above-mentioned publication, the rubber pellets are simply mixed with the higher fatty acids or/and their salts, and therefore a sufficient amount of the higher fatty acids or/and its salts is not stably attached to the rubber pellets, making it difficult to transport and weigh the rubber pellets. It has become clear that blocking occurs after such operations during storage.

The present inventors have discovered that higher fatty acids or/and their salts having 12 to 30 carbon atoms and/or their salts (hereinafter simply referred to as "higher fatty acids or/and their salts") can be stably prepared into olefinic rubber pellets (hereinafter referred to as
As a result of research into a method for adhering a sufficient amount to rubber pellets (sometimes simply referred to as "rubber pellets"), we found that when mixing rubber pellets and higher fatty acids or/and their salts, monohydric alcohols with 1 to 4 carbon atoms (hereinafter referred to as
The present invention was completed based on the finding that a sufficient amount of higher fatty acids and/or salts thereof can be stably deposited on rubber pellets by allowing the presence of alcohol (sometimes simply referred to as "alcohol").

The higher fatty acids of the present invention are saturated or unsaturated higher fatty acids having 12 to 30 carbon atoms, including lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, behenic acid, oleic acid, linoleic acid,
Specific examples include α-eleostearic acid, β-eleostearic acid, and α-linoleic acid. Further, the salts of higher fatty acids of the present invention include sodium salts, potassium salts, magnesium salts, calcium salts, zinc salts, aluminum salts,
Examples include iron salts and lithium salts. The above-mentioned higher fatty acids or salts thereof may be used alone or as a mixture. However, the use of salts of higher fatty acids is recommended.

Olefin copolymer rubbers to which the present invention is applied include ethylene, propylene, 1-butene, 1-
2 carbon atoms such as pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene
Copolymer rubber consisting of any two or more olefins selected from the group consisting of 1 to 10 α-olefins; any two or more olefins selected from the above olefins, 1,4-hexadiene, 1,6
-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-
Methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-
norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene,
6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5
-Norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-
Copolymer rubber consisting of one or more polyenes selected from polyenes such as 2,2-norbornadiene, 1,3,7-octatriene, and 1,4,9-decatriene; Any one or more polyenes selected from the above olefins. olefin and polymerizable carbon-carbon double bonds such as vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, metal salts of acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, and metal salts of methacrylic acid. copolymerized rubber with one or more monomers selected from monomers which have an oxygen atom as a constituent component; and the like. More specifically, for example, ethylene/propylene copolymer rubber, ethylene/1-butene copolymer rubber, propylene/1-butene copolymer rubber; ethylene/propylene/1,4-hexadiene copolymer rubber, ethylene/propylene/dicyclo Pentadiene copolymer rubber, ethylene/propylene/5-ethylidene-2-norbornene copolymer rubber, ethylene/1-butene/1,4-hexadiene copolymer rubber, ethylene/1-butene/dicyclopentadiene copolymer rubber, ethylene/ Examples include 1-butene/5-ethylidene-2-norbornene copolymer rubber; ethylene/vinyl acetate copolymer, ethylene/methyl methacrylate copolymer rubber, copolymer rubber of ethylene and a metal salt of methacrylic acid; In particular, any kind of monomer unit having the above olefin unit and the above polymerizable carbon-carbon double bond and containing an oxygen atom as a constituent component constituting the copolymer rubber is 90 mol% or less, especially The content is preferably 80 mol% or less.

In order to obtain rubber pellets with low stickiness from the rubber of the present invention using the higher fatty acid or/and its salt, rubber pellets are once produced, and before the pellets are agglomerated, the pellets and the finely powdered higher fatty acid are mixed together. or/and a salt thereof in the presence of an alcohol to coat the surface of the pellets. In that case, the higher fatty acid or/and its salt is about 0.05 to about 5 parts by weight per 100 parts by weight of rubber.
Parts by weight are used, preferably from about 0.1 to about 1 part by weight. If the amount exceeds about 5 parts by weight, the properties of the rubber will be impaired, and if the amount is less than about 0.05 parts by weight, the rubber pellets will not be sufficiently prevented from sticking.

The alcohol used here is a monohydric alcohol with 1 to 4 carbon atoms, and preferred examples include methanol, ethanol, propanol, isopropanol, butanol, t-butanol, s-butanol, and iso-butanol.
Among them, it is particularly preferable to use methanol and ethanol.

Alcohol is higher fatty acid or/and its salt 100%
It is recommended that it be present in an amount of about 5 to 400 parts by weight, preferably about 25 to 100 parts by weight. Of course, higher fatty acids or/
Alternatively, the salt thereof and alcohol may be mixed. The presence of alcohol allows a sufficient amount of the higher fatty acid salt and/or its salt to adhere stably to the rubber pellets.

After the mixing operation, the alcohol is evaporated by blowing with an air blower or by reducing the pressure in a container capable of reducing the pressure, thereby obtaining rubber pellets that are prevented from becoming sticky.

The higher fatty acid or/and its salt is preferably in the form of fine powder, and has a spherical diameter of usually about 300 μm or less, preferably about 100 μm or less.

Mixing of the rubber pellets and the higher fatty acid or/and its salt in the presence of alcohol is achieved by using a device such as a Henschel mixer, tumbler, or vibrator.

The rubber pellets coated with higher fatty acids and/or their salts obtained as described above can be used even after being transported by freight, by packing 25 kg of the pellets into bags, stacking the bags in 10 layers and leaving them for one month. Not sticky.

Examples will be specifically described below.

Example 1 Disc-shaped pellets of Mitsui EPT #3045 (particle size 100
g/1000 pieces) and 1.0 part by weight of calcium stearate using a Henschel mixer, first put the EPT pellets into the Henschel mixer, then add the calcium stearate.
1.0 part by weight and 0.25 part by weight of methanol were simultaneously added and mixed. After drying the obtained pellets, the amount of adhering calcium stearate was measured, and it was found that calcium stearate was stably adhering to the pellets at a ratio of 0.5% by weight.

The pellets were placed on a sieve fitted with an 80-mesh wire mesh, simulating the vibrations caused by freight transportation, etc., and the pellets were vibrated to sift out the calcium stearate that was not firmly and stably attached, and then packed into a 25 kg paper bag. They were stacked in layers and left in an atmosphere of about 25°C for one month.

When observing the degree of adhesion of pellets to the bottom bag, no pellets were observed in any case.

Example 2 Calcium stearate was previously dispersed in methanol to create a dispersion of calcium stearate/methyl alcohol = 30 parts by weight/70 parts by weight,
Disc-shaped pellets of EPT#3045 (particle size 100g/1000
) Calcium stearate 1.0 per 100 parts by weight
The dispersion liquid was weighed out in parts by weight, and both were mixed using a Henschel mixer. After drying the obtained pellets, the amount of adhering calcium stearate was measured, and it was found that calcium stearate was stably adhering to the pellets at a ratio of 0.5% by weight.

When this pellet was examined for cohesiveness in the same manner as in Example 1, no pellets were found to be attached.

Example 3 Calcium stearate-attached pellets were obtained in the same manner as in Example 1, except that methanol was replaced with ethanol. When the amount of calcium stearate attached to the pellets was measured, it was found that calcium stearate was
It was stably attached at a ratio of 0.5% by weight.

When this pellet was examined for cohesiveness in the same manner as in Example 1, no pellets were found to be attached.

Example 4 Calcium stearate-attached pellets were obtained in the same manner as in Example 1, except that methanol was replaced with butanol. When the amount of calcium stearate attached to the pellets was measured, it was found that calcium stearate was
It was stably attached at a ratio of 0.5% by weight.

When this pellet was examined for cohesiveness in the same manner as in Example 1, no pellets were found to be attached.

Comparative Example 1 Calcium stearate-attached pellets were obtained in the same manner as in Example 1 except that 0.25 parts by weight of methanol was not used. When we measured the amount of calcium stearate attached to the obtained pellets, we found that the initial amount of calcium stearate attached was only 0.15.
% by weight, and furthermore, in the agglomeration test of the pellets after sieving in the same manner as in Example 1, significant agglomeration was observed.

Claims (1)

[Claims] 1. In a method for producing olefin copolymer rubber pellets with low stickiness coated with a higher fatty acid having 12 to 30 carbon atoms or/and a salt thereof, the olefin copolymer rubber pellets and the finely powdered higher fatty acid or / and a salt thereof in the presence of a monohydric alcohol having 1 to 4 carbon atoms.