JP2003342440A - Rubber-silica mixed powder and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably improve a powder characteristic of a grafted rubber powder by adding a hydrophilic silica powder having a definite characteristic to a grafted rubber powder and to provide a rubber-silica mixed powder which satisfies fully the present situation of recent years where enhanced product performance is highly demanded. <P>SOLUTION: The rubber-silica mixed powder comprises 100 pts.mass of a grafted rubber powder and 0.001-3.0 pts.mass of a hydrophilic silica powder. The hydrophilic silica powder has an average particle diameter of the primary particle of 20-80 nm and a specific surface area of 20-below 150 m<SP>2</SP>/g. A manufacturing method therefor is also provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber-silica mixed powder containing a grafted rubber powder surface-modified with a hydrophilic silica powder. Furthermore, the present invention relates to a method for producing this rubber-silica mixed powder.

[0002]

2. Description of the Related Art A grafted rubber obtained by graft-polymerizing a rubber-like polymer as a trunk polymer with a polymerizable monomer is generally used in the form of powder to improve the impact resistance of other resins. However, it may be mixed with other resins. For example, hard resins such as polyvinyl chloride, polystyrene, polymethyl methacrylate, acrylonitrile-styrene copolymer, polycarbonate, PET, PB
This grafted rubber powder is blended in order to modify the impact resistance of engineering plastics such as T and polyacetal. However, since this grafted rubber powder has tackiness, the powders may coagulate during storage, causing so-called blocking.
In addition, the fluidity is poor due to the adhesiveness, and there is a problem that the transportation line is blocked. In particular, when the content of the rubber-like polymer in the grafted rubber is increased in order to increase the impact resistance modification effect, the above-mentioned problems of blocking and clogging of the transportation line are remarkable.

Further, this grafted rubber powder is generally produced from a grafted rubber latex by a spray drying method, a coagulation / drying method, etc. There were cases where the powder of the grafted rubber adhered to various places of the. This adhesion may cause an increase in contamination, a decrease in yield, and a decrease in productivity due to frequent cleaning. In particular, in the manufacturing method by the spray drying method, the powder of the grafted rubber is likely to adhere to the powder drying device, and these problems have been remarkable. In order to improve the blocking resistance and tack resistance of such a grafted rubber powder, the grafted rubber powder contains an inorganic powder, particularly silica (silicon dioxide).
Powders are being added. As the silica powder, for example, an example using a hydrophobic silica powder has been proposed (Japanese Patent Laid-Open No. 4-185649 and Japanese Patent Laid-Open No. 4-185649).
185646, etc.). The hydrophobic silica powder has a tentative effect on improving the powder properties of the rubber-containing graft polymer, but it is necessary to perform a surface treatment on the silica powder in order to impart hydrophobicity. Therefore, it is inevitable that the hydrophobic silica is more expensive than the hydrophilic silica, and when it is used for preventing the blocking of the grafted rubber powder, the cost becomes disadvantageous.

On the other hand, examples using hydrophilic silica powder have also been proposed (Japanese Patent Laid-Open No. 64-26663 and Japanese Patent Laid-Open No. 8-113692). For example, JP-A-64-
In Japanese Patent No. 26663, the average particle size is 10 μm (1000
A method of adding various inorganic powders of 0 nm or less to the grafted rubber is proposed, and the smaller the average particle size of the inorganic powder is, the greater the effect of improving the powder properties is.
As an example using a hydrophilic silica powder, a 10 nm hydrophilic silica powder is illustrated. In addition, JP-A-8-1
JP 13692 discloses mixing an ultrafine silica powder having an average particle size of less than 0.02 micron (20 nm) and a specific surface area of 150 to 250 m ² / g with a calcium salt fine powder to prepare an elastomer impact additive powder. Methods for improving powder properties are described.

However, when the inorganic powder to be used is a hydrophilic silica powder, the smaller the average particle size, the better, but if it is too small, the grafted rubber powder is compacted during storage. At this time, the grafted rubber powders are likely to come into surface contact with each other, and blocking is likely to occur. On the other hand, if the silica powder is too large, the number of hydrophilic silica particles decreases, and the surface coverage of the grafted rubber powder decreases. Suppressing contact between the grafted rubber powders by having a size in a certain range,
The blocking of the grafted rubber powder can be efficiently improved. Therefore, in specifying the hydrophilic silica, it is possible to highly specify the hydrophilic silica suitable for blocking prevention by specifying the primary particle size and the specific surface area. This makes it possible to specify a hydrophilic silica suitable for blocking prevention, and it has been clarified that the powder characteristics of the grafted rubber powder can be sufficiently improved without adding a calcium salt.

[0006]

The object of the present invention is to improve the powder properties of the grafted rubber powder by adding a hydrophilic silica powder having certain properties to the grafted rubber powder. It is an object of the present invention to provide a rubber-silica mixed powder that sufficiently satisfies the current state of the art, which requires high performance. Further, an object of the present invention is to add a hydrophilic silica powder during or after the drying of the grafted rubber latex and mix it, and obtain a rubber-silica mixed powder obtained without affecting the physical properties of the grafted rubber powder. An object of the present invention is to provide a rubber-silica mixed powder in which the blocking resistance of the body is improved and adhesion of the grafted rubber powder to a manufacturing apparatus in a grafted rubber manufacturing process is preferably prevented, and a manufacturing method thereof. .

[0007]

In order to solve the above problems, the present inventor has conducted extensive studies and as a result, added hydrophilic silica powder satisfying a certain average particle diameter and specific surface area to the grafted rubber powder. Therefore, it was found that the conventionally required hydrophobic treatment of the surface of the silica powder and the need for adding a calcium salt can be preferably improved in the blocking resistance and tack resistance of the grafted rubber powder, and the present invention It has arrived. That is, the present invention contains 100 parts by mass of the grafted rubber powder and 0.001 part by mass or more and 3.0 parts by mass or less of the hydrophilic silica powder, and the hydrophilic silica powder has a primary particle size of 20 nm or more and 80 nm or less. The present invention relates to a rubber-silica mixed powder having an average particle size and a specific surface area of 20 m ² / g or more and less than 150 m ² / g. In the method for producing the rubber-silica mixed powder, the hydrophilic silica powder is added during or after the drying of the grafted rubber latex, the rubber-silica mixed powder. It relates to a manufacturing method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber-silica mixed powder of the present invention comprises (1) grafted rubber powder, (2) hydrophilic silica powder,
And (3) any other inorganic powder. Hereinafter, each component will be described in detail. (1) Grafted rubber powder The grafted rubber powder used in the present invention is obtained by graft-polymerizing a rubber-like polymer as a trunk polymer with a polymerizable grafting monomer. (1-1) Trunk Polymer Examples of the rubber-like polymer that is a trunk polymer include n-
Acrylic rubber-like polymer containing butyl acrylate, 2-ethylhexyl acrylate, etc. as the main component, diene rubber-like polymer containing butadiene, isoprene, chloroprene, etc. as the main component, and silicone rubber-like substance containing organosiloxane as the main component Polymers may be mentioned. More preferably, polybutadiene and a block copolymer of 1,3-butadiene and styrene; tetraethoxysilane, γ-methacryloyloxypropyldimethoxymethylsilane,
A composite rubber of a polyorganosiloxane obtained from octamethylcyclotetrasiloxane and a (meth) acrylate such as methyl acrylate, ethyl acrylate, n-butyl acrylate or methyl methacrylate is suitable. Further, two or more kinds of these rubbery polymers may be combined, or a rubbery polymer containing a glassy polymer in the core may be used. The content of such a rubber-like polymer is, for example, based on the total mass of the grafted rubber powder,
It is suitable that the content is 40% by mass or more, preferably 50% by mass or more. When the content of the rubber-like polymer is 50% by mass or more, the effect of modifying the surface of the grafted rubber by the hydrophilic silica powder becomes more remarkable, which is particularly preferable. The rubber-like polymer is, for example, 20 ° C. or lower, preferably −8.
It is suitable to have a glass transition temperature (Tg) of 0-10 ° C.

(1-2) Grafting Monomer In the present invention, the grafting monomer to be grafted on the trunk polymer is not particularly limited as long as it is a grafting monomer which can be graft-polymerized on the trunk polymer. Examples of the monomer that can be grafted to the above-mentioned trunk polymer in the present invention include aromatic vinyl monomers,
Examples thereof include vinyl cyanide-based monomers, ethylenically unsaturated carboxylic acid-based monomers, unsaturated carboxylic acid alkyl ester-based monomers, vinyl halide-based monomers, and maleimide-based monomers. The aromatic vinyl-based monomer is not particularly limited, and examples thereof include styrene, α-methylstyrene, methyl-α-methylstyrene, vinyltoluene, divinylbenzene and the like. Of these, styrene is particularly preferable. The vinyl cyanide-based monomer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like. Of these, acrylonitrile is particularly preferable.

The ethylenically unsaturated carboxylic acid monomer is not particularly limited, but examples thereof include mono- and dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid. The unsaturated carboxylic acid alkyl ester-based monomer is not particularly limited, but for example, methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, allyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate,
Butyl methacrylate, propyl methacrylate, 2-
Examples thereof include ethylhexyl methacrylate, allyl methacrylate, and glycidyl methacrylate. The vinyl halide monomer is not particularly limited, and examples thereof include vinyl chloride and vinylidene chloride. The maleimide-based monomer is not particularly limited, and examples thereof include maleimide, N-phenylmaleimide, N-cyclohexylmaleimide, N-methylmaleimide and the like. Further, in addition to the above monomers, emulsion-polymerizable monomers such as ethylene, propylene, vinyl acetate, vinyl pyridine, etc. can also be used. These grafting monomers can be used alone or in combination of two or more.

(1-3) Polymerization Method of Grafted Rubber The polymerization method of the rubber-like polymer as the above-mentioned trunk polymer and the graft polymerization method of the obtained rubber-like polymer and the grafting monomer are not particularly limited. Usually, an emulsion polymerization method is used. Moreover, the polymerization method of these rubber-like polymers and the graft polymerization method of the obtained rubber-like polymer and the grafting monomer are carried out in separate steps using two or more stirring devices. However, both polymerization methods may be carried out in a continuous process in the same stirrer. Further, at the time of polymerization, the grafting monomer and various additives such as a polymerization initiator and an emulsifier can be added by a method such as batch addition, continuous addition, divided addition, multi-step addition, or a combination thereof. For example, a reactor equipped with a stirrer is charged with a grafting monomer which is a material of the rubbery polymer and necessary additives, and the temperature is raised to 50 to 80 ° C. During the temperature rise, a polymerization initiator, a catalyst and the like are further added to start the polymerization. About 5
After holding at 50 to 90 ° C. for 10 hours, an emulsifier is added and a grafted rubber latex is obtained from the above reaction apparatus.

The polymerization initiator added during the polymerization is not particularly limited, but examples thereof include water-soluble persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, diisopyropyrbenzene hydroperoxide and p-menthane hydro. Peroxide, cumene hydroperoxide, t-butyl hydroperoxide, methylcyclohexyl hydroperoxide, 1,1,
3,3-tetramethylbutyl hydroperoxide,
1,1,3,3-tetramethylbutylperoxy-2-
Organic peroxides such as ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-butylperoxy-3,5,5-tri-methylhexanoate It is possible to use a redox-based initiator having one component as a component. The emulsifier is not particularly limited, and examples thereof include alkali metal salts of higher fatty acids such as disproportionated rosin acid, oleic acid, stearic acid; alkali metal salts of sulfonic acid such as dodecylbenzenesulfonic acid; beef fatty acid potassium soap; Oxyethylene alkyl phenyl ether sulfate etc. can be used individually or in combination of 2 or more types. Further, the catalyst is not particularly limited, but a redox catalyst is preferable, for example. Examples of the redox catalyst include a mixture of hydrous crystalline glucose and ferrous sulfate heptahydrate; a mixture of ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, sodium formaldehyde sulfoxylate dihydrate and deionized water. Is mentioned. In addition to the components described above, a thickener such as sodium pyrophosphate; a thickener such as anhydrous sodium sulfate; a reducing agent such as sodium formaldehyde sulfoxylate dihydrate; divinylbenzene, 1
-3 Butylenedimethacrylate, allylmethacrylate, glycidylmethacrylate and other crosslinking agents; and chain transfer agents such as mercaptans and terpenes may be used as additives.

(1-4) Method for producing grafted rubber powder The grafted rubber powder in the present invention is produced by drying the grafted rubber latex obtained as described above. Specifically, the grafted rubber latex is recovered by drying, for example, by a coagulation / drying method or a spray drying method. The dried powder has, for example, a coagulation method of 50 to 1000 μm, and preferably 10 μm.
Grafted rubber powder having an average particle size of 0 to 600 μm is obtained. The coagulation / drying method is a method in which a grafting rubber latex obtained by the above-mentioned polymerization method is brought into contact with a coagulant to coagulate / dry the grafted rubber in the latex. For example, the grafted rubber latex and the coagulant are put in a stirrer, and the mixture is heated at 30 to 95 ° C for 1 to 10
Hold for about a minute to solidify the grafted rubber. afterwards,
The powdered grafted rubber can be obtained by dehydrating and drying the solidified slurry-like grafted rubber. The grafted rubber latex used here may be a single kind or a mixture of a plurality of grafted rubber latexes. Examples of the coagulant to be brought into contact with the grafted rubber latex include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, organic acids such as formic acid and acetic acid, inorganic salts such as calcium chloride, magnesium sulfate and aluminum sulfate, calcium acetate and aluminum acetate. And organic acid salts thereof. These coagulants are
It is preferably used in the form of an aqueous solution. Also, in the stage of contacting the coagulant with the grafted rubber to coagulate,
An additive such as an antioxidant can be further added. As the antioxidant, for example, triethylene glycol-
Bis [3- (3-tert-butyl-5-methyl-4]
-Hydroxyphenyl) propionate], dilauryl-3,3'-thiodipropionate and the like. This coagulation method is not particularly limited in coagulation equipment, method, conditions, etc., and any method such as a batch method of coagulating in one tank or a continuous method of continuously coagulating in two or more tanks can be used. You can

The spray drying method is a method in which the latex of the grafted rubber is directly sprayed in hot air and dried. For example, a grafted rubber latex in the form of a latex is made into droplets having an average diameter of about 30 to 200 μm, and the temperature is 50 to 300 ° C.
Spray in a drying cylinder with hot air and dry. Thereby, for example, 30 to 200 μm, preferably 50
Dry particles of ˜170 μm are obtained. In this spray drying method, the spray drying apparatus, method, conditions, etc. are not particularly limited as long as the grafted rubber present in the latex can be pulverized. Further, as a method of generating the latex droplets, any method such as a rotating disk type, a pressure nozzle type, a two-fluid nozzle type, a pressurized two-fluid nozzle type may be used. Further, the latex of the grafted rubber used may be a single latex or a mixture of a plurality of latexes. It is also possible to add an appropriate antioxidant or additive to the latex to be sprayed and then spray-dry it. Also, the capacity of the drying device used for spray drying is not particularly limited, and a drying device of any capacity can be used, from a small scale used in a laboratory to a large scale used industrially. Can be used.

(2) Hydrophilic Silica Powder The hydrophilic silica powder used in the present invention has an average particle size of primary particles of 20 nm or more and 80 nm or less and a specific surface area of 20 m ² / g or more and less than 150 m ² / g. Is to have. (2-1) Hydrophilicity The silica powder used in the present invention is a hydrophilic silica powder that has not been subjected to surface treatment such as hydrophobic treatment. This hydrophilicity may be inherent in the silica compound used, such as silicon dioxide. Specifically, for example, synthetic silica having ² or more silanol groups / nm ² on the surface of silica powder can be used. Therefore, it is possible to remove the silica powder having a hydrophobic property by the surface treatment with a silane compound or the like.

(2-2) Average particle size of primary particles The hydrophilic silica powder used in the present invention has a primary particle size of 20 nm to 80 nm, preferably 25 to 80 nm, more preferably 30 to 75 nm. It has an average particle diameter of diameter. Here, the average particle size of the primary particles refers to the size of the silica particles alone when the hydrophilic silica powder is present as the silica powder alone without secondary aggregation. Further, the average particle diameter as referred to herein is a number average particle diameter. When the average particle size of the primary particles of the hydrophilic silica powder is 20 nm or more, when mixed with the grafted rubber powder, the flowability and blocking resistance of the grafted rubber powder can be improved with high efficiency. Further, when the average particle size of the primary particles of the hydrophilic silica powder is 80 nm or less, the transparency of the molded product does not deteriorate when the grafted rubber powder is melt-kneaded with the thermoplastic resin, which is preferable. is there.

(2-3) Specific surface area Further, the hydrophilic silica powder used in the present invention has a surface area of 20 m.
² / g or more and less than 150 m ² / g, preferably 30 to 10
It has a specific surface area of 0 m ² / g. Here, the specific surface area is a surface area per unit weight of the powder, and the specific surface area in the present invention is measured by a gas adsorption method (BET method) which is measured by adsorbing gas on the surface of powder particles. To be done. When the specific surface area of the hydrophilic silica powder used in the present invention is 20 m ² / g or more and less than 150 m ² / g, blocking can be efficiently prevented, and the flowability of the rubber-containing graft polymer powder can be improved with high efficiency. It is preferable because the blocking property can be improved. (2-4) Types of hydrophilic silica powder As an example of the hydrophilic silica powder used in the present invention having such characteristics, silicon dioxide powder can be mentioned.
Specifically, Aerosil # 5 manufactured by Nippon Aerosil Co., Ltd.
0, # 90G, Nipseal E-2 manufactured by Nippon Silica Co., Ltd.
20A is mentioned. Further, these hydrophilic silica powders may be manufactured by a known silica powder manufacturing method, for example, a dry method, a wet method or the like.

(3) Other inorganic powders In order to improve the blocking resistance and tack resistance of the grafted rubber powder, it is possible to use other inorganic powders in combination with the above hydrophilic silica powder. Examples of the inorganic powder include inorganic powders containing an element selected from the group consisting of Mg, Ca, Ba and Zn, but calcium salt powders are preferable. By using silica powder in combination with other inorganic powder, the flowability and blocking resistance of the rubber-containing graft polymer powder can be improved at a lower cost. However, since the hydrophilic silica powder used in the present invention can efficiently prevent the blocking of the grafted rubber powder, it has sufficient blocking resistance and tack resistance even without these inorganic powders.

(4) Rubber-silica mixed powder The rubber-silica mixed powder of the present invention contains the above-mentioned grafted rubber powder, hydrophilic silica powder, and any inorganic powder. (4-1) Component amount of rubber-silica mixed powder The rubber-silica mixed powder contains 0.001 part by mass or more and 3.0 parts by mass or less of hydrophilic silica powder based on 100 parts by mass of the grafted rubber powder. Preferably, 0.005 to 1.0 part by mass is suitable. When the addition amount of the hydrophilic silica powder is 0.001 part by mass or more, the flowability and blocking resistance of the grafted rubber powder can be sufficiently improved, and the grafted rubber can be favorably prevented from adhering to the manufacturing apparatus. . Further, when the amount is 3.0 parts by mass or less, the physical properties inherent in the grafted rubber are not affected, and the cost is superior, which is preferable. When an inorganic powder is used in combination, the addition amount of the inorganic powder is preferably 0.01 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the grafted rubber powder. If it is 0.01 part by mass or more, a sufficient surface modifying effect can be obtained.
When the amount is 0 parts by mass or less, the physical properties inherent in the grafted rubber are not affected, which is preferable.

(4-2) Method for producing rubber-silica mixed powder The rubber-silica mixed powder of the present invention is a mixture of the above-mentioned grafted rubber powder, hydrophilic silica powder and any inorganic powder. Obtained by As a method of adding the hydrophilic silica powder to the grafted rubber powder, for example, there is a method of adding the hydrophilic silica powder during or after the drying of the grafted rubber latex. Specifically, for example, when the grafted rubber powder is produced by a coagulation / drying method, the grafted rubber powder is obtained by dehydrating / drying the coagulated slurry-like grafted rubber latex. The hydrophilic silica powder used in the present invention is introduced together with the grafted rubber into a dryer such as a fluid dryer or an airflow dryer used in this drying step, and the rubber-containing graft polymer powder and silica are incorporated in the dryer. The powder is mixed with the powder to obtain the mixed powder of the present invention. When the grafted rubber powder is produced by the spray drying method, for example, the grafted rubber latex is sprayed and dried in the drying cylinder, and at the same time, the hydrophilic silica powder is introduced into the drying cylinder in the form of an aqueous dispersion solution. Then, the grafted rubber powder and the hydrophilic silica powder are simultaneously dried and mixed by the hot air in the drying cylinder. Continuous injection of hydrophilic silica powder into the drying cylinder during spray drying not only improves the flowability and blocking resistance of the final grafted rubber powder, but also modifies the surface of the grafted rubber during drying. it can. This is preferable because it also has the effect of improving the tackiness of the grafted rubber, that is, the effect of suppressing the adhesion of the grafted rubber powder to the inner wall surface of the drying cylinder during the process of producing the grafted rubber powder. The method of introducing the silica powder into the drying cylinder is not particularly limited, but may be added to the drying cylinder by various powder feeders from the ceiling and side surfaces of the drying cylinder, or the inside of the drying cylinder may be negative. You may inhale it under pressure. Further, a drying gas, a gas for atomizing the liquid sprayed from a nozzle such as a two-fluid nozzle or a pressurized two-fluid nozzle, or a gas for cooling the disk atomizer is mixed and continuously fed into the drying cylinder. You may throw in.

[0021]

EXAMPLES The present invention will be described below based on examples. In addition, "parts" and "%" in Examples and Comparative Examples are "parts by mass" and "% by mass", respectively, unless otherwise specified.
It represents. (1) Preparation of rubber-silica mixed powder (A) Examples 1 to 3, Comparative Examples 1 to 4 (A-1) Production of rubber-like polymer 1,3-butadiene as a monomer for producing a rubber-like polymer 80 parts and 20 parts of styrene were added to a reactor equipped with a stirrer, and further 190 parts of deionized water, 1.45 parts of beef fatty acid potassium soap as an emulsifier, 0.2 part of sodium pyrophosphate as a viscosity reducing agent, polymerization initiation. 0.5 part of paramenthane hydroperoxide as an agent was added, and the temperature was raised to 57 ° C with stirring. Next, during the temperature rise, 10 parts of deionized water, a mixture of 0.3 parts of hydrous crystalline glucose as a Redox catalyst and 0.003 part of ferrous sulfate heptahydrate were added to start emulsion polymerization. . After maintaining at 57 ° C. for 8 hours to complete the polymerization, 1.45 parts of beef fatty acid potassium soap as an emulsifier was added, and a rubbery polymer latex (1,3-butadiene / styrene copolymer) was added from the inside of the reactor. A-1) was taken out.

(A-2) Production of grafted rubber latex In the above reactor equipped with a stirrer, 639 parts of the obtained rubber-like polymer latex (A-1) (213 as a solid content)
Parts), water 85 parts, and beef tallow fatty acid potassium 3.0 parts as emulsifiers were added, and the inside of the reaction apparatus was replaced with nitrogen, and then the temperature inside the reaction apparatus was raised to 70 ° C. During heating, 0.71 part of anhydrous sodium sulfate as a bloating agent was added, and then 0.3 part of sodium formaldehyde sulfoxylate dihydrate as a reducing agent was added. Then, 28 parts of methyl methacrylate and 7 parts of ethyl acrylate as a grafting monomer, and 0.15 part of cumene hydroperoxide as a polymerization initiator were continuously added over 30 minutes, and then maintained at 70 ° C. for 100 minutes. Next, 55 parts of styrene as a grafting monomer and cumene hydroperoxide of 0.
20 parts and 100 parts are continuously added over 100 minutes, and then 70 parts are added.
Hold at 120 ° C for 120 minutes. Finally, 10 parts of methyl methacrylate as a grafting monomer and 0.05 part of cumene hydroperoxide as a polymerization initiator were continuously added over 30 minutes, and then maintained at 70 ° C. for 2 hours to complete the polymerization. It was The crude grafted rubber latex (rubber content 65%) thus obtained was emulsified and dispersed in 100 parts of the grafted rubber, and triethylene glycol bis [3- (as an antioxidant was used. 3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 0.21 part and dilauryl-3,
0.63 parts of 3'-thiodipropionate was added to obtain a grafted rubber latex (A-2). The obtained grafted rubber is a grafted rubber having 1,3-butadiene / styrene copolymer as a trunk polymer and methyl methacrylate, ethyl acrylate and styrene as grafting monomers.

(A-3) Production of grafted rubber powder (coagulation / drying method) Obtained rubber-containing graft polymer latex (A-2)
(100 parts as solid content), sulfuric acid as coagulant 1.5
Was added to a reactor equipped with a stirrer. During this time, the reactor was kept at 45 ° C. with stirring. In addition, a latex of methyl methacrylate / butyl acrylate copolymer (2.0 parts as solid content) was added to the reactor. A solidified slurry was obtained by holding it at 45 ° C for 5 minutes, and the temperature was gradually raised to 85 ° C. The obtained slurry was dehydrated and dried to obtain a grafted rubber powder (A-3) having an average particle diameter of 270 µm. It was (A-4) Preparation of rubber-silica mixed powder 100 parts of the obtained grafted rubber powder (A-3) was added to Table 1
0.1 part of the hydrophilic silica powder shown in (1) was mixed to obtain a rubber-silica mixed powder.

Table 1

(B) Examples 4 to 5 and Comparative Examples 5 to 7 (B-1) Production of Rubbery Polymer 2 parts of tetraethoxysilane and γ-methacryloyloxypropyldimethoxymethyl as a monomer for producing a rubbery polymer. 0.5 parts of silane and 97.5 parts of octamethylcyclotetrasiloxane are mixed to obtain a siloxane mixture 100.
I got a part. Then 100 parts of this siloxane mixture
Sodium dodecylbenzene sulfonate as an emulsifier and dodecylbenzene sulfonic acid were added to 200 parts of deionized water in which 1 part each was dissolved. Then, after preliminarily stirring by a homomixer at 10,000 rpm, it was emulsified and dispersed at a pressure of 30 MPa by a homogenizer to obtain an organosiloxane latex. This organosiloxane latex was charged into a reactor equipped with a stirrer, stirring was started, and the mixture was kept at 80 ° C for 5 hours and then left at 20 ° C for 48 hours. After that, the pH of the organosiloxane latex was neutralized to 7.4 with an aqueous sodium hydroxide solution,
The polymerization was completed and the polyorganosiloxane was removed from the reactor.

33 parts of the obtained polyorganosiloxane
To 10 parts as solid content, 1.4 parts of polyoxyethylene alkylphenyl ether sulfate (Emer NC-35, manufactured by Kao Corporation) as an emulsifier, and 271 parts of deionized water were added. Then, after substituting with nitrogen, the temperature inside the reactor was raised to 50 ° C., 78.4 parts of n-butyl acrylate and 1.6 parts of allyl methacrylate as monomers for producing a rubbery polymer were added, and polymerization was further initiated. 0.40 parts of t-butyl hydroperoxide as an agent was added, and the mixture was stirred at 50 ° C. for 30 minutes. Then, a mixed solution of 0.002 parts of ferrous sulfate, 0.006 parts of ethylenediaminetetraacetic acid disodium salt, 0.26 parts of sodium formaldehyde sulfoxylate dihydrate and 5 parts of deionized water was added as a Redox catalyst. Radical polymerization was initiated. Then, the temperature in the reaction vessel was maintained at 70 ° C. for 2 hours to obtain a rubber-like polymer latex (B-1) which was a polyorganosiloxane / butyl acrylate / acryl methacrylate composite rubber.

(B-2) Production of Grafted Rubber Latex The obtained rubber-like polymer latex (B-1) was added with t-butyl hydroperoxide 0.05 as a polymerization initiator.
A mixture of 10 parts by weight and 10 parts of methyl methacrylate as a grafting monomer was added dropwise at 70 ° C. for 15 minutes to carry out graft polymerization. Then, it was kept at 70 ° C. for 4 hours and taken out from the reaction apparatus to obtain a grafted rubber latex (B-2). The obtained grafted rubber is a grafted rubber having a polyorganosiloxane / butyl acrylate / acryl methacrylate composite rubber as a trunk polymer and methyl methacrylate as a grafting monomer.

(B-3) Production of Grafted Rubber Powder (Coagulation / Drying Method) The obtained grafted rubber latex (B-2) (100 parts as solid content) was mixed with calcium chloride as a coagulant.
5 parts of an aqueous calcium chloride solution was added to a reactor equipped with a stirrer. During this period, the reactor was kept at 40 ° C. while being stirred. Further, a latex of methyl methacrylate / butyl acrylate copolymer (2.0 parts as solid content) was added into the reactor. Hold for 5 minutes to obtain a solidified slurry, which is gradually heated to 85 ° C., and the obtained slurry is dehydrated and dried to obtain an average particle diameter of 29.
0 μm of grafted rubber powder (B-3) was obtained.

(B-4) Preparation of rubber-silica mixed powder 100 parts of the obtained grafted rubber powder (B-3) was added to Table 2
0.1 part of the hydrophilic silica powder shown in (1) was mixed to obtain a rubber-silica mixed powder. Table 2

The composition and the like of the rubber-silica mixed powder obtained as described above are summarized in Table 3 below. The average particle size of the primary particles of the hydrophilic silica powder was measured by an electron microscope. The specific surface area of the hydrophilic silica powder was measured by the N ₂ gas adsorption method (BET method). Table 3

(2) Evaluation [Blocking resistance] In order to measure the blocking resistance of the rubber-silica mixed powder containing the grafted rubber powder and the hydrophilic silica powder of the above Examples and Comparative Examples, the following procedure was performed. A blocking measurement was performed. 20 g of the rubber-silica mixed powder obtained in the above Examples and Comparative Examples was placed in a cylindrical container, and at a block making temperature of 50 ° C. or 60 ° C., 17.5.
A block was prepared by applying a pressure of KPa for 6 hours. The obtained block was vibrated using a micro-type electromagnetic vibration sifter (manufactured by Tsutsui Rika), and the time (second) at which the block was crushed by 60% was measured. The shorter this time is, the better the blocking resistance is, and it is preferably 50 seconds or less. The measurement results are shown in Table 4. Table 4

As described above, when the rubber-silica mixed powder containing the hydrophilic silica powder of Examples 1 to 5 is used, the time required for the block to be crushed by 60% is 50 seconds or less, and the blocking prevention effect is high. I understood. On the other hand, Comparative Example 1
When the rubber-silica mixed powder containing the hydrophilic silica powder of ~ 6 is used, the time required for the block to be crushed by 60% is 5
It was longer than 0 seconds, and it was found that the antiblocking effect was low.

[Adhesion Resistance] In order to measure the effect of improving the adhesion of the rubber-silica mixed powder of the present invention, the adhesion state of the grafted rubber in the dryer during the step of drying the grafted rubber is as follows. And observed. Experimental Example 1 Using a spray dryer manufactured by Okawara Kakoki Co., Ltd., which has a drying barrel having a straight barrel portion of 3500 mm and a straight barrel portion height of 4800 mm, the above grafted rubber latex (A-2) was used in an amount of 25 kg based on the mass of the solid content. Introduced into the drying cylinder from the charging port of the straight body under the condition of / hr and spray-dried, at the same time, the primary particle diameter used in Example 4 was 30 nm and the specific surface area was 50 m ² / g.
Hydrophilic silica powder (product name: Aerosil # 50 manufactured by Nippon Aerosil Co., Ltd.) was continuously added to the inside of the drying cylinder from the charging port of the straight body of the spray dryer under the condition of 0.07 kg / hr.
After the above operation was continued for 1 hour, the state of adhesion of the wall surface inside the drying cylinder was visually evaluated. Experimental Example 2 In place of the hydrophilic silica powder used in Experimental Example 1, a silica powder having a primary particle diameter of 26 nm and a specific surface area of 102 m ² / g (manufactured by Nippon Silica Co., Ltd., trade name Nipsil ER) was used. Spray drying was carried out in the same manner as in Experimental Example 1, and the state of wall adhesion inside the drying cylinder was visually evaluated. Reference Example 1 The same procedure as in Experimental Example 1 was carried out except that the spray drying was carried out without adding the hydrophilic silica powder in the drying cylinder. The evaluation of the sticking resistance is ◯: There is little adhesion of the grafted rubber powder to the inner wall surface of the drying cylinder. X: The grafted rubber powder is often attached to the inner wall surface of the drying cylinder. It was based on. The results are shown in Table 5. Table 5

[0034]

As described above, the hydrophilic silica powder specified by the present invention is excellent in improving the powder properties of the grafted rubber powder, and even if added in a small amount, the powder properties of the grafted rubber powder can be efficiently improved. Can be improved. As described above, in the rubber-silica mixed powder of the present invention, the hydrophilic silica powder is present on the surface of the grafted rubber powder having adhesiveness, prevents the grafted rubber powders from adhering to each other, and efficiently. It is possible to improve the tack resistance and blocking resistance of the grafted rubber powder. Also, the fluidity of the grafted rubber powder is improved,
It is possible to prevent blockage during transportation. Therefore, it is possible to cope with an increase in the size of the apparatus for producing the grafted rubber powder and automation of the apparatus such as automatic weight reduction. Furthermore, the rubber-silica mixed powder of the present invention can suppress the adhesion of the grafted rubber powder in the manufacturing apparatus in the manufacturing process. In particular, when producing the grafted rubber powder by spray drying, at the same time as the latex of the grafted rubber in the drying cylinder,
By continuously charging the above-mentioned hydrophilic silica powder into the drying cylinder, it is possible to prevent the grafted rubber powder during drying from adhering to the inner wall surface of the drying cylinder. Therefore, contamination can be reduced and quality can be improved. In addition, the yield of the grafted rubber powder is improved, and the need for frequent cleaning of manufacturing equipment such as a drying cylinder is eliminated.
Productivity can be improved. Further, in the rubber-silica mixed powder of the present invention, powder characteristics can be improved without using expensive hydrophobic silica powder which requires a surface treatment, and thus the manufacturing cost can be significantly reduced. Becomes

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihiro Toritani             20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayo             Otake Office F term (reference) 4J002 BN121 BN141 BN211 BN221                       BN231 DJ016

Claims (2)

[Claims] 1. A grafted rubber powder containing 100 parts by mass and a hydrophilic silica powder in an amount of 0.001 parts by mass or more and 3.0 parts by mass or less, wherein the hydrophilic silica powder is 20 nm or more and 80 nm or more.
average particle diameter of primary particles of 20 nm ² / g or more and 1
A rubber-silica mixed powder having a specific surface area of less than 50 m ² / g. 2. The method for producing a rubber-silica mixed powder according to claim 1, wherein the hydrophilic silica powder is added during or after drying the grafted rubber latex. Silica mixed powder manufacturing method.