JPS60112841A - Enlarging method of synthetic rubber - Google Patents

Abstract

PURPOSE:To enlarge the particle size of synthetic rubber by incorporating synthetic rubber latex with acid group-contg. copolymer latex prepared by two-step polymerization of a monomer blend containing a small amount of acid group- contg. monomer and polyfunctional monomer. CONSTITUTION:Among monomer group made up of (A) 0.5-30wt% of at least one sort of acid group-contg. monomer selected from acrylic, methacrylic, itaconic and crotonic acids, (B) 99.45-35wt% of at least one sort of 1-12C alkyl acrylates, (C) 0.05-10wt% of at least one sort of copolymerizable polyfunctional monomer (crosslinkable monomer having two or more non-conjugated C=C bonds) and (D) 0-48wt% of at least one sort of monovinyl monomer copolymerizable with these components, 5-90wt% fraction except the component (A) is polymerized followed by polymerization of the rest 95-10wt% fraction containing the component (A) to prepare acid group-contg. latex with an average size 0.05-0.2mu. Next, 0.01-10pts.wt. of this latex is incorporated in 100pts.wt. of a synthetic rubber latex with a pH adjusted to >=7 to achieve the objective particle size enlargement.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an improved method for thickening synthetic rubber latex.

(Prior art 9 Synthetic rubber latex can be easily obtained by the emulsification method, and the emulsifier is usually about 0.5 to 5% of the intermediate amount of fireflies, but this formulation does not yield Z) The rubber particle diameter of the polymer latex upper is approximately 0.05-0.18μ
There is a range of degrees. However, synthetic rubbers with even larger particle diameters are required for various uses, and large particle baby rubbers have important industrial uses.

Many methods are known for completely enlarging latex-like rubber particles, and they can be broadly classified into two methods.

One method is to achieve enlargement during the rubber polymerization stage, and the other is the 75 method, in which enlargement is achieved through post-treatment after the first stage. Methods for enlarging rubber during the polymerization stage include polymerizing with as little emulsifier as possible, using a special emulsifier, seed polymerization, and increasing the monomer concentration and stirring at high speed during polymerization to coagulate. Methods for enlarging the tissue are known. Further, known methods for enlarging latex gold by post-treatment include enlarging with acid, enlarging with salt, ammonia soap method, freezing method, and enlarging with special solvents. However, each of these known methods has major drawbacks.

The biggest drawback of the method of enlarging the rubber at the stage of polymerization is that it takes an excessive amount of time for each blade. A major problem is that it is difficult to prevent raw K from growing coagulum, which usually has oversized particles.

The applicant has previously prepared a synthetic rubber latex in which the acid group-containing copolymer latex obtained by polymerizing a mixture of an alkyl acrylate and an unsaturated acid in the presence of at least one anionic surfactant is adjusted to 17 or more. We have proposed an epoch-making method in which the particle size of the synthetic rubber latex is completely enlarged by adding the compound to the synthetic rubber latex, which greatly improves the noise and drawbacks of the known enlarging methods.

As a result of further detailed studies, the present inventors found that in the method of obtaining acid group-containing copolymers, by adding a polyfunctional monomer and employing a two-stage polymerization method, it was possible to reduce the acid group content. It was discovered that the particle size of the synthetic rubber can be effectively enlarged by changing the amount of copolymer, and the invention was completed.

(Object 1 of the invention) The present invention effectively reduces the particle size of synthetic rubber latex by using an acid group-containing monomer that is less edible and by using an acid group-containing copolymer latex obtained by a two-stage polymerization method. This method provides a method for increasing the size of the body.

(Structure of the Invention) The present invention provides at least one type of synthetic rubber (A) latex (as a solid content) of 100 mtit K (solid content) adjusted to a pH of 7 or higher, at least one kind selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and crotonic acid. Acid group-containing fIi mer 0
At least one alkyl acrylate having 5 to 30 members and an alkyl group having 1 to 12 carbon atoms, at least 99.45 to 55 million yen, at least one copolymerizable polyfunctional monomer 0
05 to 10 mtl and at least one monovinyl monomer copolymerizable with these 0 to 4 amtR% (total amount 1
Acid group-containing copolymer (B) latex Q obtained by emulsion polymerization of a monomer group consisting of 00% by weight), 01 to 10.3
When enlarging the synthetic rubber by adding W (as a solid content), the acid group-containing co-11 polymer (as Bl latex) is preliminarily mixed with 5 to 90 of the monomer group, and The acid group-containing shoulder base aggregate is partially and completely polymerized, and then the remainder 95 of the monomer group containing the acid group-containing monomer is
This is a method for enlarging synthetic rubber characterized by using a copolymer latex having an average particle diameter of 0.05 to 0.2 μ obtained by polymerizing ~10% by weight of gold.

As the synthetic rubber in the present invention, polybutadiene, butadiene 50. A copolymer of ii% or more and 50% by weight or less of at least one vinyl monomer copolymerizable therewith,
In addition to chlorobrene and its copolymer, it includes an alkyl acrylate homopolymer or a copolymer consisting of 50% by weight or more of alkyl acrylate and 50% by weight or less of a vinyl monomer copolymerizable with the alkyl acrylate.

These are easily obtained by ordinary polymerization methods,
The particle size is 0.05-0.2. It is about μ. These synthetic rubbers do not require any particular regulation of polymerization conditions, and may be crosslinked with a divinyl compound or the like. Enlargement of rubber particles can be achieved simply by adding the acid group-containing copolymer latex to this synthetic rubber latex, but it is necessary that the synthetic rubber latex has a pH of 7 or higher. For example, regarding polybutyl acrylate rubber latex, sodium octylsulfosuccinate is used as an emulsifier, and potassium persulfate is used as a catalyst. No enlargement occurs at all. However, if a small amount of alkali such as potassium hydroxide is added to raise the pH to 7 or higher, a rubber having a large particle size can be easily obtained.

The acid group-containing copolymer used to enlarge the synthetic rubber in the present invention must be in the form of latex, and must contain specific acid group-containing monomers, alkyl acrylates, and polyfunctional monomers. It is essential that the monovinyl monomer is composed of a monovinyl monomer and a monovinyl monomer copolymerizable with these monomers, if necessary.

The acid group-containing monopolymers constituting the entire acid group-containing copolymer are selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and crotonic acid, and these monopolymers tI'1 can be used alone or in combination. It is used as The amount of the acid group-containing monomer in the acid group-containing copolymer is α5 to 30.

If it is less than 0.5 weight ratio, the enlarging ability is small, and if it exceeds 5 ON weight ratio, the enlarging ability becomes too strong and excessive particles exceeding 1 μm are produced, which is not favorable.

As acid group-containing monomers or similar monomers,
In addition to the above, there are cinnamic acid, maleic anhydride, butenetricarboxylic acid, etc., but their use is not practical because of their small enlargement ability.

In addition, the alkyl acrylates having an alkyl group having 1 to 12 carbon atoms constituting the acid group-containing copolymer are used alone or in combination, and the constituent amount in the acid group-containing copolymer is 99.45.
The satisfactory effect of the present invention can be obtained at a weight ratio of .about.35%.

In addition, as the copolymerizable polyfunctional monomer constituting the acid group-containing copolymer, at least two non-conjugated C=a bonds M
unsaturated acid esters of polyols such as ethylene glycol diacrylate and butanediol dimethacrylate; Examples include divinyl compounds such as divinyl esters, divinylbenzene, and unsaturated alcohol esters of unsaturated acids such as allyl methacrylate and diallyl phthalate, and these may be used alone or in combination. The above polyfunctionality I in the acid group stone-containing co-Jllj coalescence? The constituent amount of the L-mer is 0.05 to 10 deuterium. At 0.05% by weight, there is no effect of adding it, and 10
If it exceeds the heavy bullet/%, it is not suitable because cullets are likely to occur when the synthetic rubber becomes enlarged.

Furthermore, the timing of addition of the polyfunctional JP-mer is not particularly regulated;
It can be added during the first and/or second stage polymerization when producing an acid group-containing copolymer.

Aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene are examples of copolymerizable monovinyl monomers used if necessary to form the acid group-containing copolymer:
Examples include unsaturated nitrile compounds such as acrylonitrile and allyl methacrylate: alkyl (meth)acrylates in which the alkyl group has 1 to 12 carbon atoms, and these may be used alone or in combination. The amount of the monovinyl monomer in the acid group-containing copolymer is 0 to 48% by weight,
If it exceeds 48g%, the sound effects of the present invention cannot be produced.

When producing the acid group-containing copolymer used in the present invention, it is preferable to use an anionic surfactant as an emulsifier, but a nonionic surfactant may also be used. The production of the acid group-containing m copolymer is carried out by first preparing a portion of the monomer group constituting the acid group-containing co-jf1 polymer in an amount of 5 to 90% and not containing the acid group-containing monomer. Complete polymerization, and then the remaining 95 to 10 of the monomer group containing the acid group-containing monomer
It is based on a two-stage polymerization recipe in which % by weight is polymerized.

In carrying out the present invention, the acid group-containing copolymer is used in the form of a latex, but the particle size greatly affects its ability to enlarge.
A material having a diameter of 5 to 0.2 μm is used. If it is smaller than 0.05μ, its enlargement ability will be significantly reduced, and α
If it is larger than 2μ, the rubber particle diameter after enlargement will become too large, resulting in instability when graft polymerization is subsequently carried out! It becomes easier to aggregate.

Synthetic rubber latex is produced by combining this acid group @covalent in the form of latex [Does adding it enlarge the synthetic rubber? 'i is achieved, but by adding an inorganic electrolyte at the same time, the particle size of the synthetic rubber can be enlarged extremely efficiently and stably.

The amount of acid group-containing copolymer latex added is 0.0 per 1 Kfit part (solid content) of synthetic comb latex 10.
1-toMit part (as solid content), especially lc-like ILlj
: o, s ~ triple neck.

In addition, synthetic rubber latex 1 is used as a refrigerated inorganic electrolyte.
It is sufficient to use α05 to 4 parts by weight, particularly preferably 0.1 to 1 part by weight, per 00i1tft part (as solid content). It is done.

As the inorganic electrolyte, neutral inorganic salts such as potassium chloride, sodium chloride, sulfuric acid, etc. can be suitably used.

Further, this inorganic electrolyte can be added in advance during the polymerization of the synthetic rubber latex, and the same effect as when added at the time of enlargement is exerted.

(Example) The non-invention will be explained below with reference to Examples. In the examples, "part" and "chi" are respectively "M place department" and "managerial section" amount uJ
:do.

Example 1 [Synthesis of base rubber] (A-1) 1.3-butadiene 66 parts Butyl acrylate 9 Styrene 25 Potassium oleate 1.1 Potassium rosinate 1,1 Diisopropylbenzene hydroperoxide o ,z
Ferrous sulfate 0.005 Pyrophosphate sorter 0.5 Degistrose 0.3 Water 200 A mixture having the above composition was polymerized at 50°C in a 100.1 autoclave. After 9 hours, the polymerization was completed, and a rubber latex with a conversion rate of 97%, a particle size of 0.07 μm, and a pH of 9.6 was obtained.

[Synthesis of acid group-containing copolymer latex for enlargement] (B-
1) n-Butyl ester acrylate 24.8 parts triallyl siamerate 02〃 Sodium dioctylsulfosuccinate 1〃Cumene hydroxide Q, 1//Sodium formaldehyde sulfoxylate Q, 5/1 Water 200 〃 Of the above composition The mixture was heated at 70°C for 15 hours, and then heated at 70°C for a total of 1 hour with a mixture consisting of 61 parts n-butyl acrylate, 12.5 parts methacrylate #1,5, and 0.3 parts cumene hydroperoxide. The mixture was added dropwise, and then continued to be stirred for 1 hour to obtain a conversion rate of 98%, pH 2.8, and average particle size 0.0.
A 7μ copolymer latex was obtained.

100 parts (solid content) of the rubber latex (A-1) was placed in a container, and while stirring, the latex (B-1) was added in varying amounts at room temperature.

This latex was sampled immediately after stirring for 50 minutes, and sampled after being left for 5 days. After being treated with osmium tetroxide, the particle size 'i' was measured using an electronic microscope.
= 1jtl1 added.

Furthermore, the stability of the enlarged latex after being left for one month was also evaluated.

A case in which KOL was added as an electrolyte was also studied.

For comparison, all the same evaluations were carried out using a latex (B-2) having an average particle size of 0.08 .mu. obtained by polymerizing a mixture having the following composition in one step.

(B-2) n-Butyl acrylate 85.8 parts Methacrylic acid 12.5. // Oriru Methacrylate 17 Dioctylsulfosuccinate Sodium 1. O Cumene hydroperoxide 0.4 Sodium formaldehyde sulfoxylate 06
Water 200 As is clear from the results in Table 1, when obtaining the J aberration-containing copolymer for enlarging, the effect of enlarging the synthetic rubber can be improved by adding all the polyfunctional monomers and using a two-stage polymerization method. It can be seen that the stability of the obtained enlarged latex and the change in rubber particle diameter over time are small.

Example 2 As an acid group-containing copolymer latex for enlargement, the first stage contained 19 parts of butyl acrylate, 4 parts of methyl methacrylate,
It consists of 2 parts of allyl methacrylate, and the second stage is 62 parts of butyl acrylate.

A latex (B-3) consisting of 13 parts of methacrylic acid was synthesized using the same formulation as (B-1) in Example 1, and the enlargement behavior of the various synthetic rubbers shown in Table 2 was investigated.
Shown below.

Example 3 As an acid group-containing copolymer latex for enlargement, the first stage was made from 20 parts of bunal acrylate and 5 parts of methyl methacrylate9, and the second stage was made from 60 parts of butyl acrylate, 13 parts of methacrylic acid, and 2 parts of allyl methacrylate. A latex (B-4) was synthesized using the same formulation as (B-1) in Example 1, and the enlargement behavior of VC7F and Suyuzu on synthetic rubber was investigated. Table 2 shows the results.

Clothes 2 The abbreviations in Table 2 are as follows.

Bd: Butadiene BA Nibutyl acrylate St: Styrene AN: Acrylonitrile MMA: Methyl methacrylate (Effects of the invention) The present invention uses a polyg-functional monomer as a constituent component, uses a small amount of a noble substance containing an acid group, And by two-stage polymerization method! By adding the resulting acid group-containing co-polymerized latex to a fully synthetic rubber latex, it has excellent effects such as less change over time in synthesis and rubber particle diameter.

Claims (1)

[Claims] Synthetic rubber (A) latex 100 adjusted to pH 7 or higher
0.5 to 30% by weight of at least one acid group-containing monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid and crotonic acid, based on weight part (solid content) K
, at least one alkyl acrylate whose argyl group has 1 to 12 carbon atoms, 9945 to 35% by weight, and at least one copolymerizable multifunctional monomer from 0.05 to 10%
At least -f capable of copolymerizing 5J with Mr% and f'L et al.
ilt monovinyl monomer 0-48% (total amount 10%)
Acid group 9-1 copolymerized 1-ζ (B) latex 0.01 to 10 obtained by emulsion polymerization of a polymer group consisting of 0% M
When enlarging the synthetic rubber by adding Abibe (as a solid content), 5 to 90% by weight of the monomer group 91') is added in advance as the acid group-containing copolymer (B) latex.
and the part not containing the acid group-containing monomer is polymerized, and then the remaining part 95 of the monomer group containing the acid group-containing monomer is
A method for enlarging synthetic rubber, characterized in that a copolymer latex having an average particle diameter of 0.05 to 02 μm obtained by adding 105 to 10% by weight is used.