JPS595611B2 - Method for producing graft copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a graft copolymer containing an elastic backbone polymer having good powder properties and a low content of fine powder.

Graft copolymers containing elastic backbone polymers are generally produced by emulsion polymerization due to their nature, and the method of obtaining a copolymer from this graft copolymer latex is to add an acid or salt to the latex and coagulate it, and then It is usually obtained as a powder by dehydration and drying.

However, these powders are generally irregular in shape, contain fine powder, and have poor fluidity, making them prone to handling difficulties such as blocking phenomena in which powder particles solidify together during storage, and transportation lines becoming clogged due to lack of fluidity. .

Therefore, as labor savings are progressing through automation of powder weighing and larger transportation methods, there is a strong demand for improvements in the powder properties of graft copolymer particles, such as blocking and fluidity. ing. Various methods have been proposed to improve the powder properties.

For example, a method of directly spray-drying a copolymer latex to form a spheroid, a method of adjusting conditions for coagulating a copolymer latex with an acid or salt (salting-out conditions), or a method of specifying a copolymer latex. Examples include a method in which the particles are dispersed in a solvent, spheroidized, and then solidified. However, with these methods, the effect of improving the powder properties is insufficient, or even though the improvement is recognized, the inherent properties of the polymer are impaired, or the manufacturing costs, mainly for utilities, are high. At present, no good improvement method has been found. For example, in the case of spray drying, there are disadvantages such as poor thermal stability and high operating costs, such as spheroidization of latex in a specific solvent (Japanese Unexamined Patent Application Publication No. 52-111). 68285) requires the treatment of a large amount of solvent, and since the spherical latex particles are coagulated from the outside, the coagulation may be uneven and fish eyes may occur during D-loe. As a result of intensive research in view of the above drawbacks, the inventors of the present invention have mixed a copolymer latex with an organic liquid that is sparingly soluble in water and that does not dissolve the graft copolymer but can wet it, in the presence of a coagulant. discovered that a graft copolymer with good fluidity could be obtained by dispersing a coagulated copolymer impregnated with an organic liquid in water. In this case, the total volume ratio of the graft copolymer and the organic liquid in the entire mixture is less than 40 (f), and the organic liquid/graft copolymer is mixed so that the ratio is 1 to 5 (volume ratio). However, it is important to set the quantitative proportion of the polymer particles impregnated with the organic liquid to be dispersed in water as a dispersed phase as described above. The present invention will be explained in detail below. The graft copolymer used in the present invention is produced by first producing an elastic backbone polymer by conventional emulsion polymerization, and then post-polymerizing monomers that form a hard polymer into the obtained latex by emulsion polymerization. This is what you get.

The elastic backbone polymer is preferably 5 to 80 parts by weight, more preferably 5 to 80 parts by weight.
The monomer used to form the hard polymer is added in an amount of 0 to 80 parts by weight so that the total weight of the graft copolymer is 100 parts by weight. In this case, both the backbone polymer and the graft component may or may not be crosslinked. Methods for producing these copolymers are described, for example, in Japanese Patent Publication No. 45-122629, Japanese Patent Publication No. 31462-1972, and Japanese Patent Publication No. 49-1983.
-18621, Special Publication No. 50-40142, Special Publication No. 50
It is described in detail in No. 2-3667.

However, it is of course not limited to these. Examples of the elastic backbone polymer include diene polymers such as butadiene, isoprene, and chloroprene, acrylic acid alkyl ester polymers in which the alkyl group has 4 to 10 carbon atoms such as butyl acrylate, and octyl acrylate, and copolymerizable with these. Examples include copolymers with monomers. Copolymerizable monomers include aromatic vinyls such as styrene and α-methylstyrene, methacrylic acid alkyl esters such as methyl methacrylate and enal methacrylate, and methyl acrylate and ethyl acrylate with a carbon number of the alkyl group. Examples include vinyl cyanide compounds such as 1 to 3 acrylic acid alkyl esters, acrylonitrile, methacrylonitrile, and the like. Monomers forming the hard polymer include aromatic vinyls such as styrene and α-methylstyrene, methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate, acrylonitrile, methacrylonitrile, etc. Examples include vinyl cyanide compounds, vinyl chloride, vinyl halides such as vinyl bromide, and the like.

These monomers may be used alone or as a mixture of two or more monomers.
used as. Graft copolymers produced in this way and generally known include MBS resin (methyl methacrylate-butadiene-styrene resin);
ABS resin (acrylonitrile-butadiene-styrene resin), ABSM resin 5 resin (acrylonitrile-butadiene-styrene-methyl methacrylate resin), AAS
Examples include resins (acrylic acid althyl ester-acrylonitrile styrene resin) and the like. Next, the organic liquid used in the present invention is sparingly soluble in water and does not dissolve but wets the graft copolymer, and furthermore, the surface tension of the liquid is lower than the critical surface tension of the polymer, that is, preferably The surface tension at room temperature is 35 dyne/? It is necessary that the following is true.

These organic liquids vary depending on the copolymer used. Although different, generally used are paraffinic solvents such as pentane, hexane, and heptane, alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane, and alkyl substituted products thereof. These organic liquids may be used alone or in a suitable combination. Incidentally, a small amount of water-soluble liquid such as methanol or ethanol may be mixed as long as it is compatible with the above-mentioned organic liquid and satisfies the above-mentioned conditions. In the present invention, the organic liquid described above and the graft copolymer latex described above are mixed in the presence of a coagulant, and the coagulated copolymer impregnated with the organic liquid is dispersed in water. There is a method. For example, there is a method in which a mixture of an organic liquid and a copolymer latex is added to an aqueous coagulant solution under stirring, or conversely, an aqueous coagulant solution is added to a mixture of an organic liquid and a copolymer latex.

Further, the organic liquid and the copolymer latex may be added to the aqueous coagulant solution simultaneously or separately, or the aqueous coagulant solution and the organic liquid may be mixed before the copolymer latex is added. . Or, conversely, a mixture of an aqueous coagulant solution and an organic liquid may be added to the latex at the same time. Furthermore,
These steps can also be performed continuously. In either case, the latex is coagulated in the presence of an organic liquid dispersed in water;
The coagulated copolymer is impregnated with an organic liquid, and finally the copolymer impregnated with the organic liquid is dispersed in water.

Examples of coagulants used in the present invention include hydrochloric acid, sulfuric acid,
Inorganic or organic acids such as acetic acid and tartaric acid, or salts such as common salts, calcium chloride, aluminum sulfate, and Glauber's salt are preferably used.

Coagulants are generally used in the form of aqueous solutions of any concentration.
The present invention is characterized in that the total amount of the organic liquid and the graft copolymer is less than 40% by volume based on the total amount of the mixture of the organic liquid, the graft copolymer, water, and the coagulant; The purpose is to mix so that the combined volume ratio is 1 to 5.

When the total amount of organic liquid and copolymer is 40% by volume or more of the total mixture, and the volume ratio of organic liquid/graft copolymer is 5 or more, the copolymer impregnated with organic liquid is mixed in water. This makes it difficult to disperse the latex in the organic liquid, and on the contrary, the latex becomes dispersed in the organic liquid, making it impossible to achieve the object of the present invention. The volume ratio of organic liquid/graft copolymer is 1
-5, and the range of 1-3 is preferably used.

When the capacity ratio is less than 1 or more than 5, it becomes difficult to obtain spherical particles. The graft copolymer latex may be used as it is after polymerization, or may be diluted with water appropriately, but generally the copolymer concentration in the latex is 10 to 10.
50% by weight is used.

Since the organic liquid and the graft copolymer latex are mixed in the presence of a coagulant, and the total amount of the organic liquid and the graft copolymer is small compared to the total amount of the mixture, which method is used? Eventually, the coagulated fine graft copolymer particles will get wet with the organic liquid, and the polymerized fine particles sufficiently impregnated with the organic liquid will further aggregate with each other, forming a spherical shape due to the interfacial tension between the organic liquid and water. It is thought that it is converted into water and dispersed in the water.

The present invention is economically advantageous because the amount of organic liquid is small, and since the copolymer latex is not coagulated in a dispersed state in the organic liquid, coagulation is uniformly carried out during processing. It has the advantage of having fewer fish and eyes.

When mixing a copolymer latex in the presence of an organic liquid and a coagulant, appropriate stirring and shaking are necessary to obtain uniform spherical particles.

In addition, known surfactants are used to promote dispersion of the organic liquid or the copolymer impregnated with the organic liquid in water, such as alkylbenzene sulfonates, higher fatty acid salts, alkyl succinates, sorbitan higher fatty acid esters, etc. (0.01 to 0.59 t) can be added to the copolymer. Furthermore, in order to prevent particles formed into spherical shapes by the organic liquid from coalescing with each other and forming agglomerates, a suspending agent such as methyl cellulose, partially saponified polyvinyl alcohol, etc. is added to the copolymer at a concentration of 0.005 to 0. .50t) can also be added. After removing the organic liquid from the thus obtained slurry containing the spherical copolymer particles impregnated with an organic liquid, the copolymer particles are dehydrated, washed with water, and dried by a conventional method. The organic liquid is removed by heating near the boiling point at normal pressure,
It can be removed at a temperature corresponding to the boiling point under reduced or increased pressure. Heating to a temperature of 50 to 100° C. and removing the organic liquid is preferable because the heat treatment strengthens the cohesion of the aggregated particles and increases the apparent specific gravity.

The copolymer particles of the present invention maintain a spherical shape through moderate cohesion of fine particles, and the spherical shape is not destroyed during subsequent dehydration, water washing, and drying processes to produce fine powder, and the particles have good fluidity and a low bulk specific gravity. Large copolymer particles can be easily obtained.

Therefore, not only the occurrence of troubles such as blocking phenomenon and clogging of transportation lines during storage can be extremely reduced, but also the storage structure can be simplified and the storage tank and transportation can be made larger.
Furthermore, because the shape of the copolymer particles is uniform and there is less fine powder, the slurry has good dehydration properties, and the moisture content of wet cake obtained by methods such as centrifugation and suction filtration is about 20 to 50% compared to conventional products. The load on the drying process can be greatly reduced. Furthermore, since less fine powder is generated, even if the copolymer is easily combustible, the risk of dust explosion can be extremely reduced. The agglomerated copolymer of the present invention is obtained by appropriately aggregating the original latex copolymer particles.
Another feature of the present invention is that it easily returns to its original latex particle state by kneading during processing, and that even when these graft copolymers are used, for example, as an impact-strengthening agent, the effect of imparting impact strength is not impaired. There are big advantages.

The present invention will be explained below with reference to Examples.

The methods for measuring the powder properties are summarized in Table 1. Example
1 divinylbenzene 1.5 (Ff), butadiene 76%,
70 parts of a crosslinked backbone polymer consisting of 22.5% styrene was prepared by emulsion polymerization, and in the presence of the crosslinked polymer, 14 parts of styrene, 8.5 parts of methyl methacrylate, and 0.3 parts of divinylbenzene were graft-polymerized, followed by methyl methacrylate. 7.
5 parts and 0.15 parts of divinylbenzene were graft-polymerized.

The polymerization rate at each stage was approximately 100%, and the solid content in the graft copolymer latex was 35% by weight.
(Specific gravity 1.0) Pour 570 ml of hydrochloric acid water with a pH of about 2 into a glass container with an inner diameter of about 120 fL and an internal volume of 211 301!
After adding 0.07 g of polyoxyethylene sorbitan monostearate dissolved in Ll of water, 140 d of n-hexane (specific gravity 0.66, surface tension 18.4 dyne/
(177!At20°C) and disperse n-hexane under sufficient stirring.

Next, when 200 d of the above-mentioned latex was added, the viscosity of the system increased rapidly after 1 to 3 minutes, and the viscosity decreased again, producing almost spherical particles with an average particle size of 150 to 200μ, and even after stopping the stirring, The particles retained their spherical shape.
In this case, the total amount of n-hexane and graft copolymer is 22.3% by volume based on the total mixture, and the ratio of n-hexane to graft copolymer is 2 by volume.

Next, the system that became a slurry of spherical particles was heated to 65°C,
After separating n-hexane, it was dehydrated and dried to obtain polymer particles.

Table 2 shows the properties of the resin powder of this copolymer particle measured based on the method shown in Table 1.

In addition, 12 parts of the above-mentioned graft copolymer was added to 87.5 parts of polyvinyl chloride with a degree of polymerization of 700 containing 2 parts of a tin stabilizer and 1 part of a lubricant.
．． 5 parts were added and mixed.

After kneading this compound for 3 minutes with a roll at 160°C,
Press molding was carried out at 95°C for 7 minutes to prepare a test piece with a thickness of 6m11L, and the Izod impact strength of the test piece was measured and shown in Table 2. Examples 2, 3, 4 Using the graft copolymer latex used in Example 1, the amount of n-hexane used was 100ml, 200d, 300ml.
Graft copolymer aggregated particles were obtained in the same manner as in Example 1 except that m11 was used.

The powder properties and Izot impact strength are shown in Table 2. Examples 5 and 6 Copolymer particles were obtained in the same manner as in Example 1, except that the graft copolymer latex used in Example 1 was used and the type of organic liquid was changed to n-heptane or cyclohexane.

The powder properties and Izot impact strength are shown in Table 2. Comparative Example 1 The latex of Example 1 was poured into 600a of hydrochloric acid water with a pH of about 2 while stirring as in the example, and the slurry was heated to about 90°C.

The copolymer particles were obtained by dehydration, filtration, and drying, and their powder characteristics and Izotsu-Shiroshu Mizuei 1 Chu 1 Kei 9 Soul 1r;i
Comparative Example 2 The graft copolymer latex used in Example 1 was 5ν, 1-? Change the usage amount to 500ml,
Other than that, the same procedure as in Example 1 was carried out.

When the copolymer latex was added, the entire mixture coagulated into lumps, making it impossible to obtain granular particles.
At this time, the volume ratio of the total amount of n-hexane and copolymer to the entire mixture was 43.8%, and the volume ratio of n-hexane and copolymer was 7.14. Example 7 Add 600 ml of hydrochloric acid water with a pH of approximately 2 to the equipment used in Example 1.
and dissolved 0.079% of polyoxyethylene sorbitan monostearate.

Next, a mixture of 140 ml of n-hexane and 200 ml of the graft copolymer latex used in Example 1 was heated to 1200 ml.
r. p. m. The mixture was added under stirring. The viscosity of the system increases rapidly 1 to 3 minutes after addition, and after another 1 to 2 minutes, the viscosity decreases again and almost spherical aggregated particles with an average particle size of 150 to 200 μ are obtained, and the stirring is stopped. The particles also retained their shape. Next, the system which became a slurry of spherical particles was heated to 65° C. to separate n-hexane, and then dehydrated and dried to obtain polymer aggregate particles. The powder properties and Izot impact strength are shown in Table 3. Example 8 Using the equipment used in Example 1, a polymer consisting of 53.8% octyl acrylate, 30.7% butadiene, and 15.5% methyl methacrylate was used instead of the graft copolymer latex used in Example 1. Using a latex obtained by producing 65 parts of the combined product by emulsion polymerization, graft polymerizing 11 parts of styrene, 5 parts of methyl methacrylate, and 4 parts of acrylonitrile in the presence of the combined product, and then emulsion polymerizing 15 parts of methine methacrylate. Other than that, granulation was carried out in the same manner as in Example 1 by adding 140 ml of xane.

The solid content of the copolymer latex at this time was 30% by weight. Like the polymer obtained in Example 1, this produced copolymer also showed significant improvements in particle size distribution, bulk specific gravity, and fluidity.

The results are shown in Table 3. Comparative Example 3 Using the apparatus and graft copolymer latex used in Example 1, carbon tetrachloride, a liquid capable of dissolving the graft copolymer, was used as an organic liquid in place of hexane. The copolymer dissolves at the same time as the latex is added, resulting in aggregated particles of 3 to 10 m77! The resulting powder was coarse and irregular in shape, and the powder properties could not be improved.

Claims (1)

[Claims] 1. A graft copolymer latex obtained by graft polymerizing a monomer that forms a hard polymer onto an elastic backbone polymer, and a graft copolymer latex that is sparingly soluble in water. When mixing an insoluble but wettable organic liquid in the presence of a coagulant, the volume ratio of the total amount of graft copolymer and organic liquid in the entire mixture is less than 40%, and the organic liquid/graft copolymer Mix so that coalescence = 1 to 5 (volume ratio),
A method for producing a graft copolymer having excellent powder properties, which comprises dispersing the graft copolymer impregnated with an organic liquid in water. 2. The graft copolymer according to claim 1, which is sparingly soluble in water and has a surface tension of 35 dyne/cm or less at room temperature of an organic liquid that does not dissolve but can wet the copolymer. Production method. 3. The method for producing a graft copolymer according to claim 1 or 2, which comprises mixing a graft copolymer latex with a mixture of an aqueous coagulant solution and an organic liquid. 4. The method for producing a graft copolymer according to claim 1 or 2, which comprises mixing an organic liquid and a graft copolymer latex in an aqueous coagulant solution.