JP2735648B2 - Method for producing graft copolymer - Google Patents

Description

[Background of the Invention] <Industrial application field> The present invention relates to a redox-based initiator in which a monomer containing a maleimide or an N-substituted maleimide is optimally combined, thereby achieving a high graft ratio and a high degree of grafting. The present invention relates to a method for producing a graft copolymer which can be graft-copolymerized with rubber at a high polymerization conversion rate and has excellent heat resistance and impact resistance.

<Related Art> Since a resin containing maleimide is a resin having excellent heat resistance, an impact-resistant resin having a high heat deformation temperature can be produced by adding a rubber component to the resin. However, in order to produce a resin having high heat resistance and impact resistance, it is essential to use a copolymer obtained by grafting a monomer containing a maleimide as a rubber component to be blended. Also, in a polymer alloy of an ABS resin and another resin such as nylon, polycarbonate, polybutylene terephthalate, etc., in order to improve heat resistance, the rubber component is a copolymer obtained by grafting a monomer containing maleimides. It needs to be coalesced, and establishment of the polymerization technology is desired.

In general, the initiator used in the production of an ABS resin by an emulsion polymerization method is a redox-based initiator, for example, one using an organic peroxide as an oxidizing agent component. In fact, as a result of the fact that the inventor actually produced an ABS resin using an organic peroxide-based redox initiator, the molded article of the obtained resin had a high impact strength and a low thermochromic property during molding.

However, when such a redox-based initiator is used, its activity largely depends on the pH of the polymerization system. on the other hand,
When emulsion polymerization is performed using a maleimide-based monomer, a ring-opening reaction of the maleimide ring occurs on the alkaline side, and the emulsion stability is poor near neutrality. Therefore, the polymerization must be performed on the acidic side,
Therefore, it is necessary to select the best combination of redox catalysts.

As a redox catalyst, a combination of an organic peroxide as an oxidizing agent component and an iron salt (II) as a reducing agent component is further generally combined with an auxiliary reducing agent. It is said that the reaction between the iron (III) generated from iron (II) and the auxiliary reducing agent by the reaction with the oxidizing agent is rate-limiting in the radical generation mechanism. Formaldehyde sodium sulfoxylate (Rongalit) is known as a reducing agent component of a redox catalyst or as an auxiliary reducing agent. However, this is easily decomposed by an acid, so that polymerization is carried out on an acidic side. Can not be used. Saccharides are also known as auxiliary reducing agents, but also have low activity on the acidic side.

[Summary of the Invention]

<Problems to be Solved by the Invention> The present invention solves the above-mentioned problems and provides maleimide or N
-It is an object of the present invention to provide a method for producing a graft copolymer, in which a monomer containing a substituted maleimide can be graft-copolymerized to rubber at a high graft ratio and a high polymerization conversion.

<Means for Solving the Problems> The method for producing a graft copolymer according to the present invention comprises, in the presence of a rubber-like polymer latex, a monomer comprising an aromatic vinyl monomer, maleimide or an N-substituted maleimide, When emulsion copolymerizing a vinyl monomer copolymerizable therewith with a redox initiator, under acidic conditions,
The first half of the polymerization was carried out using ferrous salt and glucose as the reducing agent component of the redox initiator, and when the polymerization conversion of the monomer exceeded 60% by weight, sulfite was added as the reducing agent component. To continue the polymerization.

<Effects of the Invention> According to the present invention, by conducting polymerization under acidic conditions, maleimide or N-substituted maleimide is reacted without performing a ring-opening reaction. Even if the graft rate is improved, the polymerization conversion rate is improved under acidic conditions in the latter half of the polymerization, and the polymerization conversion rate and the graft rate are both improved to improve the yield, heat resistance and impact resistance. High resin can be manufactured.

[Specific description of the invention]

In the method for producing the graft copolymer according to the present invention, the rubbery polymer is preferably 10 to 70 parts by weight, particularly preferably 20 to 70 parts by weight.
To 60 parts by weight, an aromatic vinyl monomer, a monomer composed of maleimide or N-substituted maleimide, and a monomer mixture composed of a vinyl monomer copolymerizable therewith, preferably 90 to 30 parts by weight, Particularly preferably, in carrying out emulsion graft copolymerization with 80 to 40 parts by weight of a redox initiator, the polymerization is carried out with the reducing agent component of the redox initiator being different between the first half and the second half of the polymerization.

<Rubber-like copolymer> The rubber-like polymer is only required to be able to participate in a radical reaction, and a conjugated gen-based rubber having a double bond is desirable.

Here, as the conjugated rubber, a conjugated diene monomer component such as butadiene, isoprene, chloroprene or the like is used.
A rubber-like polymer having a glass transition temperature of 0 ° C. or less, which is contained by weight or more, is preferable. Specific examples include butadiene rubber (B
R), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and isoprene rubber (IR).

These rubbery polymers are used in a polymerization reaction in a latex state.

The rubber-like copolymer latex is generally produced by emulsion polymerization of the corresponding monomer, but the present invention uses a solid concentration of about 30 to 50% by weight and a rubber copolymer particle. Those having an average particle size of about 0.1 to 1.0 μm (or having been subjected to post-treatment (for example, particle size enlargement by partial aggregation by addition of an electrolyte) so as to have such a particle size) are preferable.

<Aromatic vinyl monomer> As the aromatic vinyl monomer which is one of the monomers for graft copolymerization, side chain and / or nucleus-substituted or unsubstituted styrene or vinylnaphthalene can be generally used. . In this case, the substituent includes a lower alkyl (for example, a C ₁ -C ₄ alkyl group, particularly a methyl group), a halogen atom (for example, a chlorine atom), a trifluoromethyl group, and the like.

Specific examples include α-alkylstyrene such as styrene and α-methylstyrene, alkyl-substituted alkylstyrene such as p-methylstyrene, and vinylnaphthalene.
These may be one kind or a mixture of two or more kinds.

The proportion of the aromatic vinyl monomer in the monomer mixture for graft copolymerization is preferably 30 to 80% by weight.

<Maleimide or N-substituted maleimide> As the N-substituted maleimide, those in which the hydrogen attached to the nitrogen atom of the maleimide is replaced with an aromatic hydrocarbon group, an alicyclic hydrocarbon group, an aliphatic hydrocarbon group, or the like can be used. It is.
Of these, aromatic hydrocarbon groups (particularly, phenyl group,
Those which are N-substituted by lower alkyl and / or halogen-substituted phenyl groups or the corresponding naphthyl groups) are preferred.

Specific examples of the N-substituted maleimide include (a) N-phenylmaleimide, N- (o-methylphenyl) maleimide, N- (m-methylphenyl) maleimide, N-
N-substituted monocyclic or condensed polycyclic aromatic maleimides such as (p-methylphenyl) maleimide and N-naphthylmaleimide, and N-substituted alicyclic alkylmaleimides such as (b) N-cyclohexylmaleimide And (c) at least one monomer selected from the group consisting of N-substituted aliphatic alkylmaleimides having an alkyl group having 1 to 10 carbon atoms. Of these, N-phenylmaleimide is particularly preferred.

The maleimide or N-substituted maleimide monomer is preferably contained in the graft copolymer monomer mixture in an amount of 5 to 65% by weight. When the content exceeds 65% by weight, the resin obtained from the copolymer latex becomes heterogeneous, and a desired graft copolymer is often not obtained.

<Vinyl monomer> A vinyl monomer is a compound having at least one vinyl group, and specifically has, for example, a cyano group, a carboxyl group, an alkyl group, a cycloalkyl group, a benzyl group, and a phenyl group. Is what you are doing.

Specific examples thereof include (a) vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; (ii) vinyl monomers containing carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and fumaric acid; ) These carboxylic acid-containing vinyl monomers include metal salts such as alkali metals and alkaline earth metals, and (d) alkyl groups having 1 to 10 carbon atoms, cycloalkyl groups, benzyl groups, and phenyl groups. Acrylates, methacrylates, itaconates,
And vinyl monomers containing a carboxylic acid ester such as fumarate and malate. These may be used alone or as a mixture of two or more kinds within a group or between groups.

The ratio of the vinyl monomer in the monomer for graft copolymerization is preferably 0 to 35% by weight.

<Catalyst> The catalyst used in the present invention comprises an oxidizing agent component, a ferrous salt,
It is a redox initiator comprising a reducing agent component consisting of glucose and sulfite. And, according to the present invention, the sulfite is used in the latter half of the polymerization.

The oxidizing component of the redox initiator includes a peroxy compound or peroxide, particularly an inorganic compound (for example,
Persulfate, perborate, hydrogen peroxide, etc.) and organic ones are known, and for emulsion polymerization, substantially water-soluble ones are used.

In the present invention, among these, organic peroxides, particularly water-soluble organic peroxides, are preferred. Examples of the water-soluble organic peroxide include cumene hydroperoxide, t-butyl peroxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide and the like. As is apparent from these examples, the “organic peroxide” referred to in the present invention includes “organic hydroperoxide”.

These can be used alone or in combination of two or more. Organic peroxide, monomer mixture 100
With respect to parts by weight, it is preferred to use from 0.05 to 1.0 part by weight.

On the other hand, as the ferrous salt of the reducing agent component, ferrous sulfate,
Preference is given to ferrous halides and ferrous cyanides such as potassium ferrocyanide. As is clear from the fact that ferrocyan potassium is one of the specific examples, the "ferrous salt" in the present invention includes complex salts and double salts as long as at least reduction to ferrous is possible. Things.

 Of these, ferrous sulfate is particularly preferred.

They can be used alone or in combination of two or more. The ferrous salt is preferably used in an amount of 0.001 to 0.05 part by weight based on 100 parts by weight of the monomer mixture.

According to the present invention, the first half of the polymerization is carried out by a redox initiator comprising a ferrous salt and glucose as a reducing agent component, and the polymerization conversion is 60% by weight or more, preferably 65% by weight.
In the latter half of the above polymerization, sulfite is added to continue the polymerization.

Glucose can be used in any form as long as it can be dissolved in water and is reducing.
That is, "glucose" in the present invention is a typical D-
In addition to glucose, it includes various isomers, particularly cyclic isomers, for example, α-D-glucopyranose and β-D-glucopyranose. Preferred glucose in the present invention is D-glucose, α-D-glucopyranose and / or β-D-glucopyranose. It is preferable to use 0.1 to 2 parts by weight of glucose per 100 parts by weight of the monomer mixture.

On the other hand, any sulfite that can be dissolved in an acidic aqueous solution and acts as a reducing agent can be used. Or a combination of two or more thereof. As is apparent from these examples, the “sulfite” in the present invention includes the “bisulfite”.

In the present invention, of these, sodium bisulfite is preferable. It is preferable to use 0.005 to 0.2 parts by weight of the sulfite based on 100 parts by weight of the monomer mixture.

<Polymerization Method> The polymerization in the present invention is an emulsion polymerization in which the emulsion system of the rubbery polymer latex is used as it is or after being modified by adding an emulsifier or the like.

The graft copolymerization itself, which comprises polymerizing the "branch" polymer monomer in the latex of the "trunk" rubbery polymer, is well known, and any suitable modification is possible in the present invention. And the polymerization can be carried out according to these well-known techniques. Equivalent to polymerizing monomers in the presence of a rubbery polymer, the "graft copolymerization" product is an ideal where all the monomers are bonded to the "backbone" polymer as "branch" polymers Although it is in any state between the case of a graft copolymer and the case where all the monomers are present as its own polymer, the graft copolymerization in the present invention also changes to such a situation. Absent.

The graft copolymerization according to the invention requires, in addition to the use of a specific redox initiator, to be carried out under acidic conditions. The "acid condition" in this case means that the pH of the rubbery polymer latex is about 3 to 7, preferably about 4 to 6.

Taking these points into consideration, one specific example of the graft copolymer of the present invention is as follows.

That is, a conjugated diene-based rubber latex is put in a reaction tank in advance, and the pH is adjusted. Conjugated diene rubber latex usually uses an alkaline carboxylate-based emulsifier, and the average particle size of the rubber is small (for example, less than 0.1 μm). Enlarges the particle size of rubber. Latex with an enlarged rubber particle diameter has an average rubber particle diameter of 0.1 to 1.0 μm.
Those in the range of m are preferred. The average particle size of rubber is 0.
If it is smaller than 1 μm, it is difficult to improve the impact resistance of the obtained graft copolymer resin, which is not preferable. 1.0μ
If it is larger than m, the graft emulsion polymerization becomes difficult, and the stability of the rubber latex decreases, which is not preferable.

The pH is adjusted by previously adjusting the pH to 3 to 6 with an acid or an acid anhydride such as sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, and acetic anhydride. For the purpose of stabilizing the latex under acidic conditions and other purposes, a sulfonate-based surfactant is used as necessary.

Usually, acidic conditions in the polymerization of the present invention are realized by this pH adjustment, but it goes without saying that pH adjustment for the purpose may be performed in order to realize the acidic polymerization conditions.

Next, the conjugated diene rubber latex is heated to a set temperature. After the temperature rise, a monomer or an emulsion thereof, and a solution of an organic peroxide or an emulsifier thereof are continuously dropped. At this time, the ferrous salt and glucose as an auxiliary reducing agent are also added dropwise as a solution. Polymerization is initiated by the addition of the reducing agent component. When the polymerization conversion rate becomes 60% by weight or more, an aqueous solution of sulfite is added to the reaction vessel while preventing oxygen oxidation, and the polymerization is continued to obtain a final graft copolymer.

<Experimental example> The following experimental example is for further specifically explaining the present invention. Note that the present invention is not limited to the following experimental examples unless it exceeds the gist. In the following examples, “parts” indicates parts by weight.

Example 1 A glass flask equipped with a stirrer, a reflux condenser, a thermometer, a monomer addition device, and an auxiliary agent addition device is charged with 100 parts (solid content conversion) of polybutadiene latex (rubber solid content concentration: 30% by weight). This polybutadiene latex has a pH of 11 and uses a carboxylate emulsifier, and the rubber has an average particle diameter of 0.09 μm. Therefore, the emulsification system is destroyed to some extent by an acid to enlarge the particle size of the rubber. Therefore, while stirring, adjust the internal temperature to 40 ° C,
Disperse 1.45 parts in 28 parts of water with a homomixer,
Add all at once. Stop stirring after 2 minutes and leave for 8 minutes. A solution prepared by dissolving 1.5 parts of eleminol (sodium alkyldiphenyl ether disulfonate) in 20 parts of water is added all at once, and stirring is started. Dissolve 0.01 part ferrous sulfate and 0.8 part glucose in 200 parts water and add. At this point the pH was 4.9 and no further pH adjustments were made.

On the other hand, 45 parts of styrene (hereinafter abbreviated as St), 30 parts of N-phenylmaleimide (hereinafter abbreviated as N-PMI),
Acrylonitrile (hereinafter abbreviated as AN) 25 parts and t
A monomer mixture consisting of 0.3 parts of dodecyl mercaptan (molecular weight regulator) was prepared (solution A).

0.625 parts of cumene hydroperoxide and 3.0 parts of eleminol (sodium alkyldiphenyletherdisulfonate) were emulsified in 30 parts of water (solution B).

0.05 parts of sodium bisulfite was dissolved in 10 parts of water, and nitrogen gas was immediately blown into bubbles (solution C).

While the stirring was continued, the temperature of the rubber latex having the enlarged particle diameter was raised. When the internal temperature reached 70 ° C., the solution A and the solution B were added dropwise while maintaining this temperature. The solution A was dropped for 3.5 hours and the solution B was dropped for 2.5 hours. The polymerization conversion 4.5 hours after the start of the polymerization was 75% by weight. Solution C was added dropwise under a stream of nitrogen. The dripping was completed in one hour. Polymerization is 6
Finished in time.

The progress of the polymerization was observed by tracking the solid content in the latex and determining the polymerization conversion of the monomer therefrom.

 The graft ratio can be represented by the following equation.

The rubber (wt%) in the crumb of the graft copolymer was calculated from the polymerization conversion.

a-weight of charged rubber (rubber-like copolymer) b-weight of charged monomer c-polymerization conversion The graft part (% by weight) in the crumb was coagulated, washed and dried after polymerization, and the acetone-insoluble part of the crumb was dried. It was determined by subtracting the rubber content.

A-Acetone-soluble matter in crumb B-Acetone-insoluble matter in crumb Example 2 Polymerization was carried out in the same manner as in Example 1 except that 0.03 parts of sodium bisulfite was used under the polymerization conditions of Example 1. .

Comparative Example 1 Under the polymerization conditions of Example 1, Solution C was not added.

Comparative Example 2 Under the polymerization conditions of Example 1, without adding glucose,
Solution C was added over 4 hours from the start of the polymerization.

Comparative Example 3 In the same manner as in Example 1 except that under the polymerization conditions of Example 1, 0.4 part by weight of glucose, 0.125 part by weight of sodium bisulfite, and 0.01 part by weight of ferrous sulfate were used for 100 parts by weight of the monomer mixture. Polymerization was performed.

The change over time of the polymerization conversion rate in the examples and comparative examples is as shown in FIG. The graft ratio is
As shown in Table 1.

Graft copolymer crumb obtained in Examples and Comparative Examples, styrene / N-phenylmaleimide / acrylonitrile copolymer (composition: St45% by weight, N-PMI 30% by weight, AN
25% by weight) and a known ABS resin (composition: polybutadiene 15.5% by weight, rubber particle diameter about 1.3 μm, AN / (St + AN) 25
% By weight) according to the blending ratio described in (Note) in Table 2, melt-kneaded and extruded with a twin-screw extruder to form a pellet of the resin composition, and a test piece for measuring physical properties by an injection molding method. Was molded. For the molded test pieces, the tensile strength, Izod impact strength (with notch), falling weight impact strength, Vicat softening point temperature, and melt flow rate were measured by the methods described in Table 2. The results were as shown in Table 2.

As is clear from the above results, the resin composition containing the graft copolymer according to the present invention has excellent impact resistance and heat resistance, and also excellent processability.

Therefore, the graft copolymer according to the present invention is useful as a molded article used in a field where impact resistance and heat resistance are required.

[Brief description of the drawings]

FIG. 1 shows the change over time of the polymerization conversion rate in Example 1 and Comparative Examples 1 and 2.

Claims (1)

(57) [Claims] (1) A redox initiator is prepared by adding an aromatic vinyl monomer, a monomer comprising maleimide or an N-substituted maleimide, and a vinyl monomer copolymerizable therewith with a redox initiator in the presence of a rubbery polymer latex. In the case of emulsion copolymerization, the first half of the polymerization was carried out using ferrous salt and glucose as the reducing agent component of the redox initiator under acidic conditions, and the polymerization conversion of the monomer exceeded 60% by weight. A process for adding a sulfite as a reducing agent component to continue the polymerization at the above stage.