JPS63182319A - Production of nitrilic graft polymer - Google Patents

Abstract

PURPOSE:To obtain the title homogeneous polymer of excellent impact resistance stably in good reproducibility, by graft-polymerizing an acrylonitrile-based monomer in the presence of a specified conjugated synthetic rubber in an aqueous medium. CONSTITUTION:At least 10wt.% conjugated diene monomer (a) such as 1,3-butadiene is emulsion-polymerized in an aqueous medium with at most 90wt.% monomer (b) copolymerizable with component (a), such as methyl (meth)acrylate or styrene, and the component (a) content is adjusted to 0.1wt.% or below to obtain a conjugated diene synthetic rubber (A). 100pts.wt. monomer (B) comprising at least 50wt.% acrylonitrile (c) and at most 50wt.% monomer (d) copolymerizable with component (c) (e.g., methyl acrylate) is graft-polymerized in the presence of 1-50pts.wt. component A by using a polymerization initiator (C) such as potassium persulfate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a high nitrile polymer with improved impact resistance using a conjugated diene synthetic rubber. More specifically, the present invention relates to an improvement in a method for polymerizing acrylonitrile and a monomer copolymerizable therewith in an aqueous medium in the presence of a conjugated diene synthetic rubber.

[Conventional technology]

Rubber-reinforced high nitrile-containing resins have high gas and vapor barrier properties and excellent solvent resistance that are inherent to high nitrile resins, as well as impact resistance. It is attracting attention as a container or packaging material.

Regarding the production method of rubber-reinforced high nitrile-containing resins, various polymerization methods have been studied and many improved techniques have been disclosed.

For example, a method in which monomers consisting of unsaturated nitrile and acrylic acid alkyl ester are polymerized by batch addition to conjugated diene/nitrile copolymer rubber (Japanese Patent Publication No. 46-250
No. 05), when unsaturated nitrile and a monomer copolymerizable with the unsaturated nitrile are polymerized in the presence of a diene-based synthetic rubber, part of the monomer swells the rubber, and the remaining monomer swells. (Japanese Unexamined Patent Publication No. 50-75294), when monomers consisting of unsaturated nitrile and aromatic vinyl are polymerized in the presence of diene-based synthetic rubber, the monomer addition rate is adjusted to the polymerization temperature. A method of adding and polymerizing at this rate (
JP-A No. 50-22086), etc.

[Problem that the invention seeks to solve]

As for the type of polymerization in this technology, emulsion polymerization, which is carried out in an aqueous medium, is generally adopted due to the ease of heat removal, ease of reaction control, and ease of post-treatment after polymerization. There is. In this emulsion polymerization method, rubber is generally produced as a latex by emulsion polymerization in advance, and monomers are added in the second stage of emulsion polymerization to graft-polymerize the rubber.

In order to control the reaction rate, the composition of the produced polymer, or the physical properties of the produced polymer in this second stage emulsion polymerization, there are various inventions described above regarding the method of adding monomers. From the perspective of removing reaction heat, the method of adding monomer batchwise involves charging a large amount of monomer at once, which causes rapid polymerization, and the polymerization machine jacket alone lacks heat removal capacity. This is disadvantageous in that an external cooler or frozen water is required. On the other hand, the method of adding the monomer in portions or continuously has the advantage that the monomer can be added at a rate that matches the heat removal capacity of the polymerization machine.

As described above, one of the factors for controlling the reaction rate in emulsion polymerization is the method of adding monomers, that is, controlling the monomer concentration within the polymerization system. However, in emulsion polymerization, various other factors such as initiator amount, emulsifier amount, and polymerization temperature have complex effects on polymerization, making it difficult to reproduce polymerization and causing quality variations in polymers from batch to batch. There was a problem that this occurred.

An object of the present invention is to solve this problem and provide a polymerization method for obtaining a nitrile polymer having excellent impact resistance with good reproducibility.

[Means for solving problems]

As a result of intensive research, the present inventors found that in a method of graft polymerization by adding acrylonitrile and monomers copolymerizable with the same to diene-based synthetic rubber in an aqueous medium, the conjugates remaining in the rubber We discovered that reducing the diene monomer concentration below a certain amount is necessary to stabilize the polymerization, that is, to obtain reproducibility of the polymerization, and that this makes it possible to stabilize the quality of the polymer. The invention was completed.

That is, the present invention uses a conjugated diene monomer lo! At least 50% by weight of acrylonitrile is copolymerized with the acrylonitrile in the presence of 1 to 50 parts by weight of a conjugated diene-based synthetic rubber consisting of 9% or less of a monomer copolymerizable with the acrylonitrile. Monomer 1 consisting of 50% by weight or less of possible monomers
00 parts by weight in an aqueous medium, the concentration of unreacted conjugated diene monomer remaining in the conjugated diene synthetic rubber is 0.1 ftI% or less. It is.

In the present invention, the impact-resistant nitrile polymer is obtained by subjecting a preformed conjugated diene synthetic rubber to a large amount of acrylonitrile and other monomer components copolymerizable with it. and in an aqueous medium,
Emulsion polymerization allows monomers and other components to be polymerized by batch, continuous, or portionwise addition at temperatures of about 0 to 100<0>C with the removal of oxygen. Preferred is an aqueous emulsion polymerization method in which monomers are added continuously or in portions.

In the present invention, the conjugated diene synthetic rubber is a latex obtained by a so-called aqueous emulsion polymerization method, and when it is used for graft polymerization, the concentration of the conjugated diene monomer remaining in the latex is reduced to 0. It is important that the amount is 1% by weight or less, so that the grafting reaction of acrylonitrile and its comonomer to the rubber proceeds in a stable manner, and the physical properties of the final polymer are also reproducible. It becomes something.

Examples of the conjugated diene monomer used in the present invention include 1,3-butadiene, isoprene, and chloroprene.
Isoprene is preferred, and monomers copolymerizable with the conjugated diene monomer include unsaturated nitriles, unsaturated carboxylic acid esters, aromatic vinyl compounds, etc.
A species or two or more species may be used.

Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like, with acrylonitrile and methacrylonitrile being preferred.

Examples of unsaturated carboxylic acid esters include esters of acrylic acid or methacrylic acid such as methyl, ethyl, propyl, butyl, etc. Particularly preferred are methyl acrylate, ethyl acrylate, methyl methacrylate, It is ethyl methacrylate.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluenes, and vinylxylenes, with styrene being preferred.

The monomers to be grafted to the rubber include one or more of acrylonitrile and monomers copolymerizable therewith, such as unsaturated carboxylic acid esters, aromatic vinyl compounds, vinyl esters, vinyl ethers, and α-olefins. It is a monomer consisting of

As for the unsaturated carboxylic acid ester and the aromatic vinyl compound, those exemplified above can be used.

Examples of the vinyl ester include vinyl acetate, vinyl propionate, and vinyl fluoride, with vinyl acetate being preferred.

In addition, examples of vinyl ether include methyl vinyl ether,
Examples include ethyl vinyl ether, propyl vinyl ethers, butyl vinyl ethers, methyl isopropenyl ether, ethyl isopropenyl ether, and the most preferred are methyl vinyl ether, ethyl vinyl ether, propyl vinyl ethers, and butyl vinyl ethers.

α-olefins include isobutyne, 2-methyl-1-
Butene, 2-methyl-1-pentene, 2-methyl-1-
hexene, 2-methyl-1-heptene, 2-methyl-1
-Octene, 2-ethyl-1-butene, 2-propyl-
Examples include 1-butene, and the most preferred is isobutyne.

The conjugated diene synthetic rubber useful in the present invention includes 1.3
-10% by weight of conjugated diene monomer, typically butadiene
It has a composition consisting of the above and a monomer copolymerizable therewith, for example, 90% by weight or less of acrylonitrile. In an aqueous medium, an emulsifier or dispersant, a polymerization initiator,
It is obtained by polymerizing at a desired temperature in the presence of molecular weight regulators, pH til adjusters, and other additives, with oxygen removed.

The monomer and other addition methods may be batch, continuous, or divided.

In the presence of the conjugated diene-based synthetic rubber previously produced by the above method, emulsion or suspension polymerization is preferred as a method for polymerizing monomers containing unsaturated nitrile as a main component. Polymerization is carried out with a polymerization initiator at a temperature of ~100°C. Monomer addition methods include batch, continuous, and divided methods, but continuous or divided addition is preferred for the purpose of controlling the heat of the polymerization reaction and making the composition of the produced polymer uniform. , polymerization initiator, molecular weight regulator, pH! The PI conditioner and other additives may be added continuously or in portions, if necessary.

The amount of conjugated diene synthetic rubber used is the total monomer weight 10
The amount is approximately 1 to 50 parts by weight relative to 0 parts by weight.

In general, as the relative proportion of rubber components in the final polymer increases, impact strength increases, but gas and vapor barrier properties decrease somewhat, so the amount of rubber that provides the physical properties appropriate for the intended use is determined. Just use it.

The amount of acrylonitrile to be supplied and the monomer copolymerizable therewith is at least 50% based on the total weight of the monomers.
It is preferable that the unsaturated nitrile is contained in an amount of at least 60% by weight, particularly preferably about 60 to 90% by weight.

In the present invention, it is important to keep the concentration of conjugated diene monomer remaining in the rubber latex obtained by emulsion polymerization as low as possible, and preferably 0.
The content shall be 1% by weight or less.

As a method for removing the residual monomer, a general method such as a method of removing under vacuum or a method using bubbling with nitrogen gas may be used.

By using the rubber latex obtained in this way, the stability of polymerization, that is, the reproducibility, is improved in the subsequent reaction of grafting a monomer mainly composed of acrylonitrile onto rubber. Conversely, if the concentration of conjugated diene monomer is 0.
If it exceeds 1% by weight, the polymerization reaction will not be stable, and the reaction will be delayed depending on the amount of conjugated diene monomer, resulting in poor reproducibility, as well as the structure and physical properties of the resulting polymer. It will also have a negative impact.

When polymerizing monomers in the presence of rubber, polymerization initiators (or catalysts) that can be used include peracid catalysts such as persulfuric acid, peracetic acid, and perphthalic acid, and persalts such as potassium persulfate. Catalyst, hydrogen peroxide, benzoyl peroxide, i8#1 chlorobenzoyl, brombenzoyl peroxide, naphthyl peroxide,
Peroxides such as acetyl peroxide, benzoylacetyl peroxide, lauryl peroxide, succinyl peroxide, di-t-butyl peroxide, dicumyl peroxide, cumyl hydroperoxide, t-butyl peroxide, sodium peroxide, barium peroxide, etc. oxide catalyst, alkyl hydroperoxide such as t-butyl hydroperoxide,
For example, there are azo catalysts such as azobisisobutyronitrile, which can be used alone or in combination of two or more.

The preferred polymerization method in the present invention is an aqueous emulsion polymerization method, and emulsifiers that can be used include myristic acid, lauric acid,
Sodium and potassium salts of palmitic acid, oleic acid, stearic acid, etc., sodium, potassium and ammonium salts of lauryl sulfate, cetyl sulfate, oleyl sulfonic acid, stearyl sulfonic acid, sulfated castor oil, laurylamine hydrochloride, stearylamine hydropropylene. These include higher amine salts such as amide, and polymeric substances such as polyvinylpyrrolidone, sodium polyacrylate, and methylcellulose.

The polymer product is obtained in the form of a latex, and the polymer is coagulated by a conventionally known method, such as a coagulation method using an electrolyte or a solvent, or a freezing method, and then washed with water and dried to obtain a polymer.

Plasticizers, stabilizers, lubricants, dyes and pigments, fillers, etc. can be added during or after the polymerization, if necessary.

The polymer produced by the method of the present invention is a thermoplastic resin that can be easily thermoformed by conventional molding methods using known thermoplastic materials, such as extrusion molding, injection molding, blow molding, etc. High barrier properties against gas,
It has excellent solvent resistance as well as excellent impact resistance, making it particularly useful as a packaging container material for bottles, films and other types of liquids and solids.

〔Example〕

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

All "parts" and "%" in the examples are based on weight.

Example 1 (A) Production of conjugated diene type rubber latex A mixture consisting of the following components was placed in a stainless steel polymerization reactor to remove oxygen and polymerized at 56° C. for 15 hours with stirring.

Acrylonitrile 40 parts Butadiene-1,360 Fatty acid soap 2.4 Azobisisobutyronitrile 0.3 Tododecyl mercaptan
0.5 water
The 200# monomer conversion rate was 90%, and the solids concentration of the latex was 30%.

Further, the concentration of residual butadiene in the latex was 2% by weight at the end of polymerization.

(B) Removal of butadiene in rubber latex Nitrogen was bubbled through the rubber latex to give a butadiene concentration of 0.1% by weight (=1000pp+m).

(C) Production of graft polymer Using the rubber latex obtained in step B above, a graft polymer was produced according to the following recipe.

Water 235 parts Acrylonitrile 70 parts Methyl acrylate 30# Latex of B above 33〃 (solid content 10 parts) Sodium dioctysulfosuccinate 1. O part Polyvinylpyrrolidone 0.4 # Potassium persulfate 0.06 part n-dodecyl mercaptan 1.0 part These raw materials were charged into a polymerization reactor, oxygen was removed, and polymerization was carried out at 60° C. with stirring.

During the polymerization, samples were taken every hour, and the reaction rate of the monomers was determined from the concentration of unreacted monomers.

The results are shown in Table 1.

Also, aluminum sulfate was added to the obtained latex to coagulate the polymer, which was recovered and dried.

Since the polymer was obtained in the form of a powder, it was roll-kneaded at 160°C and then pressed at 175°C and 10100 (/aJ G) to create a pressed sheet and an Izodig test piece. Further, Mal tIndex was measured using a sample obtained from a rolled sheet. These physical properties are also shown in Table 1.

Examples 2 to 3 Using the rubber latex obtained in Example 1-(^), the residual butadiene concentration in the rubber latex was reduced to 0.07 weight 9A (・700 ppm) by the method of Example 1-(B). and 0
．． Two types of rubber latexes with a concentration of 0.05% (.500 ppm) were prepared, and graft polymers were produced in the same manner as in Example 1-(C). The results are shown in Table 1.

Comparative Example 1 Using the rubber latex obtained in Example 1-(A) containing 2% by weight without removing residual butadiene, a graft polymer was prepared by the method of Example 1-(C). Manufactured. The results are shown in Table 1.

Comparative Examples 2 to 4 The rubber latex obtained in Example 1-(A) was used in Example 1-
3 treated with method (B) and with different concentrations of residual butadiene
I created the seeds of rubber latin. Using this rubber latex, graft polymers were produced by the method of Example 1-(C). The results are shown in Table 1.

From the results in Table 1, it can be seen that when the butadiene monomer concentration in the rubber latex is less than O.1 wt%, there is no effect on the reaction rate, but when it exceeds O.1 wt%, a delay in the reaction is observed, and the butadiene concentration The delay increases as the amount increases, indicating that the butadiene monomer remaining in the rubber latex has some form of adverse effect on the reaction.

Furthermore, as shown in Table 1, it is recognized that as the reaction rate is delayed, the amount of polymerizer scale produced also increases and the polymerization yield deteriorates.

Table 2 shows the physical properties of the polymer. Example 1 in which the concentration of butadiene remaining in the rubber latex was kept within the range of the present invention.
~30 The physical properties of the polymer are stable, as evidenced by the stabilization of the reaction, but the MeIt Index values, which indicate processability, of the polymers obtained in Comparative Examples 1 to 4 decrease due to reaction delay. There is a trend, and the Izodi shadow value is also unstable and in the direction of decline. Also, the optical property Yellow
The ss Index value also tends to deteriorate due to the delay in reaction time.

〔Effect of the invention〕

By controlling the concentration of the residual conjugated diene monomer in the rubber latex to 0.1% by weight or less according to the method of the present invention, the grafting reaction of acrylonitrile and a monomer copolymerizable therewith to the rubber can be carried out at a faster reaction rate. Table 2: Physical properties of polymers [A] ASTM-D256
-01238ASTM-01295 was achieved, and the physical properties of the resulting polymer were also stable.

In addition, as a polymerization method, a method is generally adopted in which monomers or other raw materials are added continuously or in portions to adjust the structure of the resulting polymer. If the reaction rate is influenced by the level of the residual butadiene concentration in the latex, the structure of the polymer cannot be controlled, that is, the desired physical properties cannot be obtained.

The present invention is also an effective method for such polymerization methods.

Claims (1)

[Claims] In the presence of 1 to 50 parts by weight of a conjugated diene synthetic rubber consisting of 10% by weight or more of a conjugated diene monomer and 90% by weight or less of a monomer copolymerizable therewith, at least 50% by weight or more of acrylonitrile is added. When 100 parts by weight of a monomer consisting of 50% by weight or less of a monomer copolymerizable with the acrylonitrile is polymerized in an aqueous medium, the concentration of unreacted conjugated diene monomer remaining in the conjugated diene-based synthetic rubber is A method for producing a nitrile graft polymer, characterized in that the content is 0.1% by weight or less.