JP3154539B2 - Method for producing silicone rubber latex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyorganosiloxane latex used as a rubber source for impact-resistant resins and as a raw material for aqueous emulsion paints.

[0002]

2. Description of the Related Art As an emulsion polymerization method of polyorganosiloxane, U.S. Pat. No. 2,891,920 discloses a method of mixing a polysiloxane precursor, a surfactant, a polymerization catalyst and water and heating the mixture while stirring to obtain a latex. Is disclosed. However, in this method, a polyorganosiloxane latex having a fine particle diameter of 0.1 μm or less could not be obtained, and the particle diameter distribution was wide.

US Pat. No. 3,294,725 discloses aliphatic substituted benzene sulfonic acid, aliphatic sulfonic acid, aliphatic substituted naphthalene sulfonic acid and the like as a catalyst for emulsion polymerization of polyorganosiloxane. Even if a catalyst for use was used, a polyorganosiloxane latex having a fine particle diameter of 0.1 μm or less could not be obtained, and the particle diameter distribution was wide.

US Pat. No. 3,433,780 discloses a method for producing a colloidal suspension of celsesquioxane and describes that fine particles can be formed. However, the organosiloxanes and siloxanes intended in the present invention are disclosed. There is no disclosure of a mixture comprising a system-based crosslinking agent and a siloxane-based graft-linking agent.

US Pat. No. 4,146,499 discloses a process for preparing a fine latex of a low molecular weight polyorganosiloxane oil using an oil-soluble surfactant. Also, U.S. Pat.No. 4,620,878 discloses that a polyorganosiloxane having a polar functional group and an emulsifier insoluble in the polyorganosiloxane are emulsified and dispersed in a concentrated state and then poured into a large amount of water to form a fine emulsion. A method of obtaining is disclosed. Further, Japanese Patent Application Laid-Open No. Sho 62-141029 discloses a method for producing a microemulsion of 0.15 μm or less by adding an emulsion comprising diorganosiloxane, a surfactant and water to a polymerization medium comprising water and a polymerization catalyst. ing.

[0006]

However, US patents
No. 4,146,499 does not give any suggestion about the mixtures according to the invention because of the high use of emulsifiers with respect to the polyorganosiloxane. The method described in U.S. Pat. It was not something. Further, according to the method described in JP-A-62-141029, the amounts of the emulsifier and the polymerization catalyst used are 0.15 to 6 times as large as those of the diorganosiloxane, and only the emulsion having a wide particle size distribution can be obtained. Therefore, it was difficult to reduce the coloring of the graft polymer or a resin composition obtained by mixing the graft polymer with another resin.

In view of such circumstances, the present inventors produce a polyorganosiloxane latex suitable for the production of a graft polymer, wherein the polyorganosiloxane latex has a reduced adverse effect of coloring by an emulsifier and an acid catalyst. As a result of intensive studies on the method, the present invention has been reached.

[0008]

Gist of the present invention SUMMARY OF THE INVENTION The organosiloxane consists siloxane crosslinking agent and siloxane graft-linking agent organosiloxane mixture 10
Latex prepared by preliminarily stirring a mixture of 0 parts by weight, an emulsifier, and water (hereinafter referred to as “latex A”)
Is dropped into an aqueous acid solution at a temperature of 60 ° C. or higher to polymerize
Of polyorganosiloxane latex by
A latex dripping rate of 5 parts by weight per minute
The following is the organosiloxane-based mixture at the end of dropping
/ (Acid + emulsifier) weight ratio in the range of 100/2 to 12
The method for producing a polyorganosiloxane latex (hereinafter referred to as "latex B") having a number average particle diameter of 0.1 μm or less and a standard deviation of the particle diameter of 0.07 μm or less.

Examples of the organosiloxane used in the present invention include various organosiloxane cyclics having three or more membered rings, and among them, those having a three to six membered ring are preferred. Specifically, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, etc. And these may be used alone or as a mixture of two or more. The amount of the organosiloxane in the organosiloxane mixture is usually at least 50% by weight, preferably at least 70% by weight.

As the siloxane-based crosslinking agent, a trifunctional or tetrafunctional silane-based crosslinking agent such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra Butoxysilane or the like is used.
Particularly, a tetrafunctional crosslinking agent is preferable, and among them, tetraethoxysilane is particularly preferable. The amount of the crosslinking agent used in the organosiloxane-based mixture is usually 0.1 to 30% by weight, preferably 0.5 to 10% by weight.

The siloxane-based graft-linking agent is represented by the following formula:

[0012]

Embedded image

(In each formula, R ¹ represents a methyl group, an ethyl group, a propyl group or a phenyl group, R ² represents a hydrogen atom or a methyl group, n represents 0, 1 or 2, and p represents a number of 1 to 6. )
A compound capable of forming the unit represented by is used.

(Meth) which can form a unit of the formula (I-1)
Acryloyloxysiloxane can form an effective graft chain because of its high grafting efficiency, and is advantageous in terms of exhibiting impact resistance.

Methacryloyloxysiloxane is particularly preferable as a unit capable of forming the unit of the formula (I-1). Specific examples of methacryloyloxysiloxane include β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyl Examples thereof include ethoxydiethylsilane, γ-methacryloyloxypropyldiethoxymethylsilane, and δ-methacryloyloxybutyldiethoxymethylsilane.

Examples of the unit capable of forming the unit of the formula (I-2) include vinyl siloxane, and specific examples include tetramethyltetravinylcyclotetrasiloxane.
What can form the unit of the formula (I-3) include γ-mercaptopropyldimethoxymethylsilane, γ-mercaptopropylmethoxydimethylsilane, γ-mercaptopropyldiethoxymethylsilane and the like.

The amount of the grafting agent used in the organosiloxane mixture is usually 0.05 to 10% by weight.
And preferably 0.1 to 5% by weight.

In the present invention, latex A is first produced by adding an emulsifier and water to an organosiloxane-based mixture consisting of an organosiloxane, a siloxane-based crosslinking agent and a siloxane-based grafting agent.

As the emulsifier, a usual anionic emulsifier or a nonionic emulsifier is used. The anionic emulsifier is selected from sodium alkylbenzene sulfonate, sodium lauryl sulfonate, sodium sulfosuccinate, sodium polyoxyethylene nonylphenyl ether sulfate, potassium alkenylcarboxylate, sodium N-lauroylsarcosine, potassium oleate, and the like. Used emulsifiers are used. Particularly, sulfonic acid emulsifiers such as sodium alkylbenzene sulfonate and sodium lauryl sulfonate are preferable. As the nonionic emulsifier, polyoxyethylene nonyl phenyl ether, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether and the like are used.

These emulsifiers are used in the range of 0.05 to 5% by weight based on the organosiloxane mixture. If it is less than 0.05% by weight, the dispersion state becomes unstable,
If it is used in an amount exceeding 5% by weight, the coloring of the graft polymer caused by the emulsifier becomes excessive. Therefore, the amount of the organosiloxane mixture and the water added to the emulsifier are usually 1.5 to 9 times the amount of the organosiloxane mixture. Preferably, the range is twice as large. . If the amount of water to be added is less than this range, the dispersion state becomes unstable, and a polyorganosiloxane latex having a stable particle diameter tends to be not obtained. Also, when more water is added than this range, the concentration of the resulting polyorganosiloxane decreases, so that it is unsuitable as a raw material for graft polymerization, and also unsuitable as a raw material for coatings because of the large amount of water to be evaporated. become.

The method of mixing the organosiloxane-based mixture, the emulsifier and the water includes mixing by high-speed stirring and mixing by a high-pressure emulsifier such as a homogenizer.
The method using a homogenizer is a preferable method because the dispersion of the particle diameter of the polyorganosiloxane latex becomes small. .

In the present invention, the latex A thus obtained is treated with an aqueous acid solution at a temperature of 60 ° C. or higher.
A method is employed in which the polymerization is carried out by dropping at a rate of 5 parts by weight or less per minute so that the weight ratio of the organosiloxane mixture / (acid + emulsifier) at the end of the dropping is 100/2 to 12.

Examples of the acid catalyst used in the aqueous acid solution include sulfonic acids such as aliphatic sulfonic acid, aliphatic substituted benzenesulfonic acid and aliphatic substituted naphthalenesulfonic acid, and mineral acids such as sulfuric acid, hydrochloric acid and nitric acid. These acid catalysts are used alone or in combination of two kinds. Among these, aliphatic substituted benzenesulfonic acid is preferable because of excellent stabilizing action of the organosiloxane latex, and n-dodecylbenzenesulfonic acid is particularly preferable. Further, when n-dodecylbenzenesulfonic acid and a mineral acid such as sulfuric acid are used in combination, coloring due to the emulsifier component of latex B can be reduced.

The amount of the acid catalyst is determined by the relationship between the amount of the organosiloxane in the finally obtained latex B and the amount of the emulsifier. That is, the weight ratio of the organosiloxane mixture / (acid + emulsifier) in the polyorganosiloxane latex B at the end of the dropping of the latex A is from 100/2 to 100/2.
It is determined to be 12. If the amount of the acid catalyst is less than this range, a sufficient polymerization rate for obtaining a polyorganosiloxane having a number average particle size of 0.1 μm or less cannot be obtained.
On the other hand, if it is more than this range, the standard deviation of the polyorganosiloxane particles in the latex B becomes large,
The graft polymer is not preferable because coloring derived from the acid catalyst is observed.

The temperature of the aqueous acid solution is an important factor for determining the particle size of the polyorganosiloxane, and it is necessary that the temperature be 60 ° C. or higher. If the temperature is lower than 60 ° C., the dissociation degree of the acid catalyst is low, and the organosiloxane, the siloxane-based cross-linking agent and the siloxane-based graft crossing agent cannot come into contact with the aqueous acid solution to effectively generate silanol.

In the present invention, a method of polymerizing an organosiloxane by dropping latex A into an acid aqueous solution at a rate of 5 parts by weight or less per minute is employed.

The organosiloxane mixture present in the pre-stirred latex A contacts the acid catalyst to form silanol and dissolves in the water, and the silanol reaches the acid catalyst or the micelle of the acid catalyst and the emulsifier. In order for the condensation reaction in the micelle to proceed, it is necessary to sufficiently reduce the rate of dropping the latex A. If latex A is dropped at a rate higher than the rate at which the organosiloxane-based mixture forms silanol and dissolves in water, the condensation reaction of the silanol progresses even in the dropped latex A droplets. The organosiloxane particles have a non-uniform particle size distribution. That is, when the dropping rate exceeds 5 parts by weight per minute, the particle size distribution of the polyorganosiloxane particles increases, and the standard deviation increases.

In the present invention, the silanol generated when the organosiloxane-based mixture comes into contact with the aqueous acid catalyst solution is as follows:
The acid reaches micelles of an acid catalyst existing in water, and undergoes a condensation reaction by dehydration by the acid catalyst to produce polyorganosiloxane. Acid-catalyzed micelles are of very small size and are advantageous for producing particles that are small, have small standard deviations, and have excellent monodispersity. The heating time of the mixture of latex A and the aqueous acid solution is usually 3 hours or more after the completion of the dropping. The silanol generated from the organosiloxane reacts almost completely by this heating. At this stage, the latex B is neutralized with an alkaline substance such as caustic soda, caustic potash, and an aqueous ammonia solution to stop the condensation reaction.
If the temperature is kept at a temperature of 30 ° C. or less for a long time, the crosslinking reaction between the silanols proceeds and the crosslinking density increases. Therefore, in order to increase the crosslinking density of the polyorganosiloxane, the reaction is carried out at a high temperature of 60 ° C. 5 hours to 1 at the following temperature
It may be held for about 00 hours.

Hereinafter, the present invention will be described by way of examples. Evaluations were made by the following methods. The particle size of the polyorganosiloxane in latex B was measured by a dynamic light scattering method. This measurement is a method utilizing the fact that particles in the latex have Brownian motion. When the particles in the latex are irradiated with a laser beam, the particles show fluctuations in accordance with the particle diameter. By analyzing this fluctuation, the particle diameter can be calculated. In this embodiment, the DLS-70 of Otsuka Electronics Co., Ltd.
Using type 0, the number average particle diameter (μm) and the standard deviation (μm) of the particle diameter distribution were determined.

The degree of swelling was determined by adding polyorganosiloxane to 23
The weight of toluene absorbed by the polyorganosiloxane when immersed in toluene at 48 ° C. for 48 hours was determined as a value obtained by dividing the weight of the polyorganosiloxane before immersion by the weight of the polyorganosiloxane.
The gel content was determined by dissolving the polyorganosiloxane in toluene
It was determined by extracting at 3 ° C. for 48 hours. For the measurement of the degree of swelling and the gel content, polydimethylsiloxane obtained by dropping latex B into isopropanol, coagulating and drying was used.

[0031]

【Example】

Example 1 Two parts of tetraethoxysilane, 0.5 part of γ-methacryloyloxypropyldimethoxymethylsilane and 97.5 parts of octamethylcyclotetrasiloxane were mixed to obtain 100 parts of an organosiloxane compound. To this was added 300 parts of distilled water in which 0.67 part of sodium dodecylbenzenesulfonate was dissolved, and the mixture was stirred at 10,000 rpm with a homomixer.
After stirring for a minute, the mixture was passed twice through a homogenizer at a pressure of 300 kg / cm ² to obtain a stable premixed organosiloxane latex A.

On the other hand, 10 parts of dodecylbenzenesulfonic acid and 90 parts of distilled water were poured into a separable flask equipped with a cooling condenser to prepare a 10% by weight aqueous solution of dodecylbenzenesulfonic acid.

While the aqueous solution was heated to 85 ° C., latex A was added dropwise over 2 hours, and after the completion of the addition, the temperature was maintained for 3 hours and cooled. The reaction was then held at room temperature for 12 hours and neutralized with aqueous sodium hydroxide.
The latex B thus obtained was dried at 170 ° C. for 30 minutes and the solid content was determined to be 18.2% by weight. The degree of swelling, the gel content, the number average particle diameter and the standard deviation of the particle diameter distribution were determined for latex B, and the results in Table 1 were obtained.

Example 2 In Example 1, a mixed aqueous solution of 5 parts of dodecylbenzenesulfonic acid, 5 parts of sulfuric acid and 90 parts of distilled water was used as the acid aqueous solution, and the other conditions were exactly the same as those in Example 1 and the latex B was used. Was manufactured. The solid content of the obtained latex is 18.0% by weight, the degree of swelling is 17.2, and the gel content is 85.0%.
5%, the number average particle diameter was 0.03 μm, and the standard deviation of the particle diameter distribution was 0.03 μm .

Examples 3 and 4 and Comparative Examples 1 and 2 Latex B was produced in the same manner as in Example 1, except that the concentration of the aqueous solution of dodecylbenzenesulfonic acid was changed. The results are shown in Table 1. When the concentration of dodecylbenzenesulfonic acid was 1% by weight, the number average particle size was large, and when the concentration was 20% by weight, the standard deviation of the particle size distribution was large.

Examples 5-6 and Comparative Example 3 Latex B was produced in the same manner as in Example 1, except that the temperature of the aqueous solution of dodecylbenzenesulfonic acid was changed. The results are shown in Table 1. When the temperature of the aqueous acid solution was 55 ° C., the number average particle size was large.

Examples 7 and 8 and Comparative Example 4 Latex B was produced in the same manner as in Example 1 except that the rate of dropping latex A was changed.
The results are shown in Table 1. When the dropping rate was 8 parts per minute, the standard deviation of the particle size distribution of latex B was large.

Examples 9 to 16 Latex B was prepared in the same manner as in Example 1 except that the composition of latex A was changed as shown in Table 2.
Was manufactured. Table 2 shows the results.
1 shows that fine particles having a small standard deviation of the particle size distribution can be obtained even when the type of the emulsifier is changed. Further, from Examples 12 and 13, when the ratio of the organosiloxane mixture / distilled water in latex A was increased,
It was found that the particle size of the polyorganosiloxane in the latex B was large. Further, from Examples 14 to 16, it was found that decreasing the amount of tetraethoxysilane, which is a siloxane-based crosslinking agent, in the organosiloxane-based mixture reduced the gel content and increased the degree of swelling.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

According to the method of the present invention, a fine polyorganosiloxane latex having a small particle diameter and a small standard deviation, that is, excellent in monodispersity can be obtained. This polyorganosiloxane latex allows the graft polymerization with the vinyl monomer to proceed smoothly, and also allows the graft polymer to be suppressed from coloring.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08G 77/04 C08L 83/04

Claims (2)

(57) [Claims] 1. A latex obtained by preliminarily stirring and emulsifying a mixture of 100 parts by weight of an organosiloxane-based mixture comprising an organosiloxane, a siloxane-based crosslinking agent and a siloxane-based grafting agent , an emulsifier, and water at a temperature of 6.
Polymerization by dropping into an aqueous acid solution at 0 ° C or higher
The method for producing a polyorganosiloxane latex according to
Therefore, the dropping rate of the latex is 5 parts by weight or less per minute, and the organosiloxane-based mixture / (acid + emulsion)
A method for producing a polyorganosiloxane latex having a number average particle size of 0.1 μm or less and a standard deviation of the particle size of 0.07 μm or less, the weight ratio of which is within the range of 100/2 to 12) . 2. The method according to claim 1, wherein the acid is selected from the group consisting of aliphatic sulfonic acids, aliphatic substituted benzenesulfonic acids, aliphatic substituted naphthalenesulfonic acids, sulfuric acid, hydrochloric acid and nitric acid. the method of.