KR20040065101A - Process for preparation of impact resistant styrene resin having an excellent rigidity and environmental stress crack resistance - Google Patents

Abstract

PURPOSE: Provided is a continuous method for preparing an impact resistant styrene-based resin having excellent rigidity, environmental stress crack resistance, extrusion processability and vacuum moldability. CONSTITUTION: The method for preparing an impact resistant styrene-based resin comprises the steps of: (1) forming a mixed solution containing a butadiene-based rubbery polymer and a styrene monomer; (2) adding a molecular weight modifier to the mixed solution and initiating graft copolymerization; and (3) further introducing a styrene monomer and polybutene or polyorganosiloxane after the mixed solution obtained from step (2) experiences a phase transition and carrying out graft copolymerization.

Description

PROCESS FOR PREPARATION OF IMPACT RESISTANT STYRENE RESIN HAVING AN EXCELLENT RIGIDITY AND ENVIRONMENTAL STRESS CRACK RESISTANCE}

The present invention relates to a method for producing an impact resistant styrene resin having excellent rigidity and environmental stress crack resistance (ESCR). More specifically, the method for producing an impact resistant styrene resin comprising the step of adding a molecular weight regulator and graft copolymerization of the butadiene-based rubber polymer to a mixed solution containing a styrene monomer, the time point when the butadiene-based rubber polymer phase transition The present invention relates to an impact resistant styrene resin characterized by graft copolymerization by adding a styrene monomer, polybutene, and polyorganosiloxane.

Rubber modified styrene resin is a thermoplastic resin obtained by graft copolymerization of styrene monomers in the presence of a rubber polymer, which is one of the disadvantages of styrene resins. Extruded sheets have been used in various fields requiring impact resistance, but their use in various applications has been limited due to low environmental crack resistance.

In particular, environmental cracking resistance is known as one of the very important properties in the thermoplastic resin used as a food container or a refrigerator inner material, and the production technology of rubber-modified styrene resin having excellent environmental cracking resistance has been studied. In addition, resins having excellent environmental crack resistance have recently been increasingly used in the form of thin film molding according to the characteristics of the market as the molded products are gradually enlarged and highly functionalized.

To meet these demands, resin manufacturing methods that are excellent in environmental cracking resistance to date have not balanced the demands for rigidity, impact resistance, environmental cracking resistance and vacuum forming, so that when the resin is excellent in rigidity, There is a decrease in environmental cracking.

In order to solve this problem, a method of reducing the amount of rubbery polymer or adjusting the size is used, but the impact resistance is lowered. The present invention is to provide a method for imparting excellent mechanical strength and vacuum formability without affecting the environmental cracking resistance in the production of a molded article requiring environmental cracking resistance.

The present invention, in consideration of the problems of the prior art, while maintaining the characteristics such as environmental cracking resistance and impact resistance, while producing excellent impact-resistant styrene resin composition and styrene resin excellent in rigidity, extrusion processability and vacuum moldability, etc. It is an object to provide a method.

In order to achieve the above object, the present invention is a method for producing a styrene resin,

A first step of preparing a mixed solution containing a butadiene rubber polymer and a styrene monomer;

Adding a molecular weight regulator to the mixed solution to initiate graft copolymerization; And

A third step of graft copolymerization by further administering a styrene-based monomer and polybutene or polyorganosiloxane after a point in time at which the mixed solution of the second step is phase shifted

It provides a method for producing an impact resistant styrene resin comprising a.

In addition, the present invention

As styrene resin composition containing butadiene rubber polymer, styrene monomer, molecular weight regulator, polybutene and polyorganosiloxane,

The polybutene and polyorganosiloxane provide an impact resistant styrene resin composition, wherein the butadiene-based rubber polymer is added after a phase change phase on the styrene resin.

The present invention provides a continuous impact-resistant styrene resin prepared by a method comprising graft polymerization of a styrene monomer or a styrene monomer with a vinyl monomer copolymerizable with the styrene monomer in the presence of a butadiene rubber polymer. In order to harmonize stiffness and environmental cracking resistance, a molecular weight modifier is added to the rubber polymer and the monomer mixture solution, and graft copolymerization is carried out in a continuous process. A) low molecular weight polybutene or b) polyorganosiloxane or a) and b) are added at the same time so as to have excellent rigidity while maintaining environmental cracking resistance and impact resistance.

Particularly, the present invention uses a polyorganosiloxane together with polybutene to attain a part of the monomer component and a low molecular weight polybutene dosing time after the phase transition time, so as to achieve harmony of environmental cracking resistance and excellent rigidity. Configured invention.

Hereinafter, the impact resistance styrene resin production method of the present invention will be described in more detail.

The first step is to prepare a mixed solution containing a butadiene-based rubber polymer styrene monomer. The butadiene-based rubber polymer is a polybutadiene prepared using butadiene, is dissolved in the following styrene monomer and a solvent and introduced into the reactor to be dispersed on the styrene resin.

The amount of the butadiene rubber polymer is preferably 3 to 10% by weight of the butadiene rubber polymer and the styrene monomer. If the rubber polymer is less than 3% by weight, the impact resistance of the produced resin is significantly lowered. If the rubber polymer is more than 10% by weight, it is advantageous for environmental cracking resistance, but the rigidity is lowered, which is not preferable.

In addition, the butadiene-based rubber copolymer is preferably 5 to styrene solution viscosity of 200 to 300 cp at 25 ℃. If the styrene solution viscosity is out of the above range, the environmental cracking resistance and stiffness are not balanced.

Next, the styrene monomers include alkyl styrenes such as styrene, α-methyl styrene, o -methyl styrene, p -methyl styrene, m -methyl styrene, ethyl styrene, i -butyl styrene and t -butyl styrene; And o-bromostyrene, p - and one or more selected from croissant the group consisting of halogenated styrene such as styrene in combination-bromostyrene, m-bromostyrene, o-chroman as styrene, p-chroman as styrene, m May be used, preferably styrene. In addition, it may further include a vinyl monomer copolymerizable with the styrene monomer.

The content of the styrene monomer or the vinyl monomer copolymerizable with the styrene monomer is preferably 90 to 97% by weight of the butadiene rubber polymer and the styrene monomer, and serves to dissolve the butadiene rubber polymer. .

Next, the second step is a step of starting the graft copolymerization after adding the molecular weight regulator to the mixed solution of the first step.

The molecular weight modifier may be selected from the group consisting of n -octyl mercaptan, n -dodecyl mercaptan, t -dodecyl mercaptan, and α-methyl styrene dimer. The graft copolymerization is initiated by adding the molecular weight regulator to the mixed solution of the first step and adding the molecular weight regulator to the reactor and raising the temperature. The temperature of the reactor is preferably adjusted to 120 ~ 150 ℃.

Next, the third step is a step of graft copolymerization of the styrene resin by adding a styrene-based monomer and polybutene or polyorganosiloxane after the phase transition time of the mixed solution of the second step.

The polybutene is preferably polybutene having a low molecular weight, in particular, a number average molecular weight of about 500 to 3000 to improve environmental cracking resistance. If the number average molecular weight is less than 500 or more than 3000, the environmental crack resistance and the rigidity cannot be balanced, and the addition amount is preferably 0.01 to 2.0 parts by weight based on 100 parts by weight of the mixed solution of the first step, more preferably. Is 0.5 to 1.5 parts by weight.

In addition, the polyorganosiloxane is preferably used at the same time as the polybutene, improves the final resin surface to improve the environmental cracking resistance. Polyorganosiloxane is a polymer containing the repetition of the structural unit represented by following formula (1).

(Formula 1)

Herein, R 1 to R 4 each independently represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an alkyl group such as isopropyl, an alicyclic hydrocarbon group such as a cyclohexyl group, an aromatic group such as a phenyl group or a benzyl group, or the above substituents. It may be a substituent containing a hydroxyl group, an alkoxy group, an amino group, an amide group, an epoxy group, a carboxyl group, a halogen group, an ester group and the like. However, preferred is dimethyl polysiloxane containing methyl groups.

The suitable viscosity range of the polyorganosiloxane is 10 to 100 cps, preferably 0.01 to 0.1 parts by weight based on 100 parts by weight of the mixed solution of the first step. Secondary processing, that is, may be used in addition to the final polymer, but considering the environmental cracking resistance it is very desirable and effective to add directly to the polymerization process.

In this step, it is advantageous for environmental cracking resistance, impact resistance, and rigidity to simultaneously inject styrene-based monomers together with polybutene and polyorganosiloxane after the phase transition point. In particular, the amount and timing of the styrene monomer to be added after the phase transition point affects the rigidity of the final resin.

In the third step, the amount of the styrene-based monomer is preferably added in an amount of 20 to 50 parts by weight, in particular 30 to 40 parts by weight, after the phase transition point.

In the present invention, the phase transition point means a point in which the rubber phase is dispersed in the styrene resin phase as the initial mixture solution is polymerized. If the total amount of the polymerization initiator is added before the phase inversion point (in the initial stage of the polymerization reaction) as in the prior art, the size of the rubber particles decreases and the impact strength is significantly reduced.

The weight ratio of the styrene graft copolymer copolymerized with the butadiene-based rubber polymer initially added is 1: 3.5 (the time when the conversion rate of the initial monomer is 1.5 to 3.5 times the amount of the rubber polymer) before being dispersed on the styrene resin. Since the phase of the rubber particles is a relatively small amount, it is difficult to see that the phase transition is completed and there is a problem that does not improve the rigidity. Since the phase transition is almost completed before the time when the weight ratio is 1: 3.5, the phase transition time is preferably spring to the time when the weight ratio is 1: 1.5 to 3.5.

In the production method of the present invention, an impact resistant styrene resin can be prepared by adding a polymerization initiator, a molecular weight regulator, a solvent, a plasticizer, an antioxidant, or an ultraviolet absorber used in conventional polymer polymerization.

Peroxy ketals such as 1,1-bis ( t -butyl peroxy) -3,3,5-trimethyl cyclohexane as the polymerization initiator; Dialkyl peroxides such as di- t -butyl peroxide and 2,5-dimethyl-2,5-di (t-butyl peroxy) hexane; Diacyl peroxides such as dibenzoyl peroxide; peroxy esters such as t -butyl peroxy isopropyl carbonate; Kenon peroxides, such as a cyclohexanone peroxide; And azo compounds such as 2,2′-azobisisobutylonitrile, and may be selected from one or more thereof, and are preferably organic peroxide-based polymerization initiators.

The polymerization solvent may be used to lower the viscosity of the polymerization solution, and may be used in an amount of 10 to 25 parts by weight based on 100 parts by weight of the raw material monomer, for example, one or more selected from the group consisting of toluene, ethylbenzene, and xylene. have.

The production process used in the present invention may be continuous or batch bulk polymerization, solution polymerization, or block-suspension polymerization, and continuous bulk polymerization or solution in that there is no problem of productivity and quality uniformity and water pollution. Polymerization is preferred.

Preferred embodiments of the invention

a) 3 to 10 parts by weight of butadiene rubber polymer;

b) In preparing a thermoplastic impact resistant styrene resin at a weight ratio of 90 to 97 parts by weight of a styrene monomer or a styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the mixed solution of a) and b) may be a molecular weight regulator. Prepared by copolymerization,

c) 20 to 50 parts by weight of component b) based on 100 parts by weight of the mixed solution of a) and b) after the injected mixed solution has a phase transition time; 0.01-2.0 parts by weight of low molecular weight polybutene; 0.01 to 0.1 parts by weight of polyorganosiloxane is included to prepare a shock-resistant styrene resin by graft polymerization by continuous solution polymerization.

More specifically, the present invention is a continuous method for producing a styrene resin using a stirred reactor,

i) 3 to 10 parts by weight of a butadiene rubber polymer having a 5% styrene solution viscosity of 200 to 300 cps at 25 ° C .;

Ii) 90 to 97 parts by weight of a styrene monomer or a vinyl monomer copolymerizable with the styrene monomer;

Preparing a raw material mixed solution by dissolving in 100 parts by weight of a monomer mixed solution mixed in a weight ratio of the mixed solution;

b) graft polymerization of the mixed solution of step a) into a first reactor of a continuous polymerization apparatus in which two or more stirred reactors are connected (preferably in series);

c) graft polymerization of the copolymer of step b) into a second reactor; And

d) devolatilizing and pelletizing the final copolymer of step c);

As a method for producing a styrene resin containing

After the phase transition point in the polymer production step of step a) or b) or c), 20 to 50 parts by weight of styrene monomer, 0.01 to 2.0 parts by weight of low molecular weight polybutene, based on 100 parts by weight of the mixed solution of step a). It provides a method for producing an impact resistant styrene resin, characterized in that at least 0.01 part to 0.1 parts by weight of polyorganosiloxane and polyorganosiloxane.

The average particle diameter of the rubber particles in the impact-resistant styrene resin prepared by the above manufacturing method is excellent in environmental cracking resistance when it is set to 5.0 ㎛ or more, and considering the environmental cracking resistance and rigidity, the rubber particles of the styrene resin It is preferable that an average particle diameter is 6.0-10.0 micrometers.

In addition, the average molecular weight of the impact-resistant styrene resin produced through the above production method is preferably 190,000 or more is preferable for environmental cracking resistance and rigidity.

The styrene resin composition of the present invention is a styrene resin composition comprising a butadiene rubber polymer, a styrene monomer, a molecular weight regulator, polybutene and polyorganosiloxane, wherein the polybutene and polyorganosiloxane are the butadiene rubber polymer. Is a styrene resin composition which is impact resistant, characterized in that it is added after the time point at which phase change occurs on the styrene resin.

The styrene resin composition has excellent environmental cracking resistance, impact resistance and extrusion processability, is recyclable, and particularly, has excellent rigidity and vacuum formability, and thus impact resistance for manufacturing sheet molded articles of thin films using the same. It is applied at the time of manufacture of styrene resin.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, an Example is for illustrating this invention and is not limited only to these.

Example 1

Butadiene-based rubber polymer (25 ° C., 5% styrene solution viscosity 250 cp) 7.0 parts by weight, styrene 79.0 parts by weight, and 14.0 parts by weight of ethylbenzene were prepared, and then a t -dodecyl mercaptan was prepared as a molecular weight regulator. 0.015 parts by weight was added. The mixed solution was introduced into a continuous polymerization apparatus in which four stirred reactors were connected in series and subsequently graft polymerized.

In addition, 30 parts by weight of the styrene-based monomer, 1.5 parts by weight of low molecular weight polybutene (number average molecular weight 920) and 0.05 parts by weight of dimethyl polysiloxane (25 ° C. viscosity of 25 cp) per 100 parts by weight of the monomer mixture solution had an initial polymerization conversion rate. After about 27%, the batch was added.

The temperature at the inlet of the polymerization apparatus was 128 ° C and the temperature at the outlet was 148 ° C. The final copolymer mixed solution was sent to a devolatilization bath to remove unreacted monomer and solvent at 230 ° C. and 20 torr, and then pelletized to obtain a final impact resistant styrene resin. After the injection molding of the resin obtained as described above to measure the physical properties as shown in Table 1 below.

[How to measure]

Tensile Strength and Elongation: An injection test piece of 19 × 180 × 3.2 mm was prepared and measured according to ASTM D256.

-Izod impact strength: 12.7 × 64 × 6.35 mm injection test specimen was prepared and measured in accordance with ASTM D256.

-Environmental crack resistance test (ESCR): After applying 0.7% strain to the surface of injection specimen, apply salad oil to a certain thickness, and leave it at room temperature (25 ℃) for 2 hours and measure elongation according to ASTM D256.

-ESCR relative elongation% = (Elongation after ESCR test / initial elongation) * 100, ESCR relative elongation% is better the higher the measured value.

Example 2

It was prepared by the same composition and method as in Example 1, and prepared by adding no low viscosity polybutene at the time of addition.

Example 3

It was prepared by the same composition and method as in Example 1, and prepared by adding no dimethyl polysiloxane upon addition and addition.

Example 4

It was prepared by the same composition and method as in Example 1, and prepared by adding an additional amount of low viscosity polybutene to 3.0 parts by weight.

Comparative Example 1

The same composition and method as in Example 1 were carried out, and the entire amount was initially added without a process of addition of an impact-resistant styrene resin.

Comparative Example 2

It was prepared by the same composition and method as in Example 1, and prepared by adding low viscosity polybutene and dimethyl polysiloxane at the time of addition.

TABLE 1

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Tensile Strength (kg / cm ² ) 310 314 311 291 283 317 Tensile Elongation% 110 113 107 113 98 104 Izod impact strength (kg cm / cm) 9.6 9.4 9.5 9.9 8.7 9.2 ESCR Relative Rate% 60.0 17.6 34.6 64.0 59.4 15.4

As described above, the styrene-based resin prepared by the present method can be recycled while maintaining characteristics such as environmental crack resistance and impact resistance, and has excellent effects such as rigidity, extrusion processability, and vacuum forming.

Claims (15)

In the manufacturing method of the styrene resin, A first step of preparing a mixed solution containing a butadiene rubber polymer and a styrene monomer; Adding a molecular weight regulator to the mixed solution and initiating graft copolymerization; And A third step of graft copolymerization by further administering a styrene-based monomer and polybutene or polyorganosiloxane after a point in time at which the mixed solution of the second step is phase shifted Method for producing an impact resistant styrene resin comprising a. According to claim 1, wherein the phase of the second phase of the mixed solution is the time when the weight ratio of the butadiene-based rubber polymer introduced in the first step and the styrene-based graft copolymer copolymerized in the second step is 1: 1.5 to 3.5 Method for producing an impact resistant styrene resin, characterized in that. The method of claim 1, wherein the mixed solution of the first step further comprises a vinyl monomer copolymerizable with a styrene monomer. The method of claim 1, wherein the third step is to further copolymerize the vinyl monomer copolymerizable with the styrene monomer after the time point at which the mixed solution is phase-transformed to graft copolymerize the impact resistant styrene resin. The method of claim 1, wherein the butadiene-based rubber polymer of the mixed solution of the first step is 3 to 10% by weight, and the styrene monomer is 90 to 97% by weight. The method of claim 1, wherein the styrene-based monomer of the third step is 20 to 50 parts by weight based on 100 parts by weight of the mixed solution of the first step. The method of claim 1, wherein the polyorganosiloxane has a viscosity of 10 to 100 cp and 0.01 to 0.1 parts by weight based on 100 parts by weight of the mixed solution of the first step. The method of claim 1, wherein the polybutene has a number average molecular weight of 500 to 3000, and is 0.01 to 2.0 parts by weight based on 100 parts by weight of the mixed solution of the first step. The method of claim 7, wherein the polyorganosiloxane is represented by the following formula (1): [Formula 1] Herein, R1 to R4 are each independently a substituent selected from the group consisting of H, an alkyl group, an alicyclic hydrocarbon group, a phenyl group and a benzyl group. The method of claim 1, wherein the mixed solution of the first step further comprises at least one selected from the group consisting of a polymerization initiator, a solvent, a plasticizer, an antioxidant, and an ultraviolet absorber. The method of claim 1, wherein the styrene-based monomer is alkyl styrene or halogenated styrene. i) 3 to 10 parts by weight of a butadiene-based rubber polymer having a 5% styrene solution viscosity of 200 to 300 cps at 25 ° C .; Ii) 90 to 97 parts by weight of a styrene monomer or a vinyl monomer copolymerizable with the styrene monomer; Preparing a raw material mixed solution by dissolving in 100 parts by weight of a monomer mixed solution mixed in a weight ratio of the mixed solution; b) graft polymerization of the mixed solution of step a) at a reactor temperature of 120 to 150 ° C. into a first reactor of a continuous polymerization apparatus in which two or more stirring reactors are connected; c) graft polymerization of the copolymer of step b) into a second reactor; And d) devolatilizing and pelletizing the final copolymer of step c); As a method for producing a styrene resin containing After the phase transition point in the polymer production step of step a) or b) or c), 20 to 50 parts by weight, 0.01 to 2.0 parts by weight of low molecular weight polybutene, based on 100 parts by weight of the mixed solution of step a) A method for producing an impact resistant styrene resin, characterized in that at least 0.01 to 0.1 parts by weight of polyorganosiloxane and parts. As styrene resin composition containing butadiene rubber polymer, styrene monomer, molecular weight regulator, polybutene and polyorganosiloxane, The polybutene and polyorganosiloxane are impact resistant styrene resin composition, characterized in that the butadiene-based rubber polymer is added after the point of phase transformation on the styrene resin. 14. The impact resistant styrene resin composition according to claim 13, wherein the styrene monomer further comprises a vinyl monomer copolymerizable with the styrene monomer. 15. The impact resistant styrene resin composition according to claim 14, wherein the polybutene has a number average molecular weight of 500 to 3000.