JP2010053295A - Processing aid for styrene elastomer, styrene elastomer composition and molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing aid having good dispersibility in a styrene elastomer and improving moldability of the styrene elastomer, and a styrene elastomer composition containing the processing aid. <P>SOLUTION: The processing aid for the styrene elastomer contains an alkyl (meth)acrylate polymer composed mainly of an alkyl (meth)acrylate unit having an alkyl group carbon number of ≥2 and having a mass-average molecular weight of 150,000-20,000,000. The styrene elastomer composition contains the processing aid and the styrene elastomer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a processing aid for styrene elastomer that improves the molding processability of a styrene elastomer, a styrene elastomer composition containing the processing aid, and a molded body thereof.

Thermoplastic elastomers are materials that exhibit rubber elasticity without requiring a vulcanization step, and are attracting attention in the fields of automobile parts, home appliance parts, electric wire coverings, footwear, sundries, etc. Currently, various materials such as olefins, urethanes, esters, styrenes, and vinyl chlorides have been developed as thermoplastic elastomers.
Among thermoplastic elastomers, styrene elastomers are excellent in flexibility, cold resistance, moisture absorption resistance, etc., and can be easily formed into a molded product that expresses rubber elasticity. In addition, it is put into practical use in various fields such as industrial products such as automobile parts, home appliance parts, building materials, civil engineering materials, medical supplies, sports equipment, and various containers.

Among styrene-based elastomers, styrene-butadiene-styrene block type, styrene-isoprene-styrene block type, styrene-ethylene-butylene-styrene block type and the like are rich in flexibility and exhibit good rubber elasticity at room temperature. In addition, the hydrogenated styrene-based elastomer has improved heat resistance and weather resistance. Since these styrene elastomers have low melt tension at the time of molding, there is a problem in moldability.
Patent Documents 1 and 2 propose a method of adding an alkyl (meth) acrylate polymer having a long-chain alkyl group to a polyolefin resin as a method for improving the molding processability of the polyolefin resin. However, no method for improving the molding processability of the styrene elastomer is disclosed.
JP-A-8-302098 JP-A-9-255816

  An object of the present invention is to provide a processing aid that has good dispersibility in a styrene-based elastomer and improves the molding processability of the styrene-based elastomer, a styrene-based elastomer composition containing the processing aid, and a molded product thereof. Is to provide.

As a result of intensive studies, the present inventors have found that an alkyl (meth) acrylate polymer having an alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl group as a main component and having a mass average molecular weight of 150,000 to 20 million. It has been found that by adding to a styrenic elastomer, molding processability can be improved without impairing the surface appearance of the resulting molded article.
That is, the processing aid for styrene elastomer of the present invention is an alkyl (meth) acrylate having an alkyl group having an alkyl group having 2 or more carbon atoms as a main component and a mass average molecular weight of 150,000 to 20 million. Contains a polymer. The alkyl (meth) acrylate polymer preferably contains an alkyl (meth) acrylate unit having 2 to 6 carbon atoms in the alkyl group as a main component.

Moreover, the styrene-type elastomer composition of this invention contains the said processing aid for styrene-type elastomers and a styrene-type elastomer.
The molded product of the present invention can be obtained by molding the above styrene elastomer composition.

The processing aid for styrene elastomer of the present invention has good dispersibility in the styrene elastomer, and can improve the molding processability of the styrene elastomer.
The styrenic elastomer composition of the present invention is excellent in moldability and does not impair the surface appearance of the resulting molded article.
The molded product of the present invention is excellent in surface appearance.

Hereinafter, the present invention will be described in detail.
The alkyl (meth) acrylate polymer of the present invention is mainly composed of an alkyl (meth) acrylate unit having an alkyl group having 2 or more carbon atoms, and has a mass average molecular weight of 150,000 to 20 million.
Dispersibility in a styrene-type elastomer becomes favorable by having as a main component an alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl group. The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate unit is preferably 2 to 13, more preferably 2 to 6, from the balance of dispersibility in the styrene elastomer and powder characteristics as a processing aid.

Examples of the alkyl (meth) acrylate having 2 or more carbon atoms in the alkyl group, which is a raw material constituting the alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl group, include, for example, ethyl (meth) acrylate and n-propyl (Meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-methylbutyl (meth) acrylate, 3 -Methylbutyl (meth) acrylate, 3-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate , Sil (meth) acrylate, dodecyl (meth) acrylate, t- butyl cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, stearyl (meth) acrylate.
These monomers may be used individually by 1 type, and may use 2 or more types together. Among these monomers, n-butyl methacrylate and isobutyl methacrylate are preferable because dispersibility in the styrene-based elastomer is improved.

The alkyl (meth) acrylate polymer of the present invention may contain other monomer units other than the alkyl (meth) acrylate unit having an alkyl group having 2 or more carbon atoms as necessary.
Examples of other monomers that are raw materials constituting other monomer units include methyl (meth) acrylate; (meth) acrylic acid; aromatic vinyl units such as styrene, α-methylstyrene, and chlorostyrene. Monomer; vinyl cyanide monomer such as (meth) acrylonitrile; vinyl ether monomer such as vinyl methyl ether and vinyl ethyl ether; vinyl carboxylate monomer such as vinyl acetate and vinyl butyrate; ethylene, propylene, isobutylene, etc. Olefins; diene monomers such as butadiene, isoprene, dimethylbutadiene; 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6 Photostabilizing group-containing monomers such as 1,6-tetramethylpiperidine; vinyl chloride, vinylidene chloride, Kka vinyl, and halogen-containing monomers such as vinylidene fluoride.
These monomers may be used individually by 1 type, and may use 2 or more types together.

The content of the alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl (meth) acrylate polymer (100% by mass) is preferably 50% by mass or more, and more preferably 70% by mass or more. .
When the content of the alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl group is 50% by mass or more, the dispersibility in the styrene elastomer is good.

The alkyl (meth) acrylate polymer of the present invention is obtained by polymerizing a monomer component mainly composed of an alkyl (meth) acrylate having an alkyl group having 2 or more carbon atoms by radical polymerization or ionic polymerization. Can do. As the polymerization method, radical polymerization is preferred.
Examples of the polymerization method of the monomer component by radical polymerization include known polymerization methods such as a bulk polymerization method, a suspension polymerization method, a solution polymerization method, and an emulsion polymerization method. Especially, since an alkyl (meth) acrylate type polymer is obtained with a powder form or a granular form, emulsion polymerization is preferable. A known method can be used for the emulsion polymerization.

Various known emulsifiers can be used for the emulsion polymerization. As the emulsifier, anionic emulsifiers such as sulfonic acid salt compounds, sulfuric acid salt compounds, and phosphoric ester salt compounds are preferable. An emulsifier may be used individually by 1 type and may use 2 or more types together.
A known polymerization initiator can be used for the emulsion polymerization. Examples of the polymerization initiator include persulfate compounds such as potassium persulfate and sodium persulfate; organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide and benzoyl peroxide; azobisisobutyronitrile. An azo compound such as: a redox initiator in which the persulfate compound or organic peroxide described above is combined with a reducing agent. Among these, potassium persulfate and sodium persulfate are preferable.

Although superposition | polymerization temperature is based on the kind of initiator, it is 40-80 degreeC normally.
Examples of the method for powderizing the latex of the alkyl (meth) acrylate polymer obtained by emulsion polymerization include a coagulation method and a spray drying method.

The mass average molecular weight of the alkyl (meth) acrylate polymer of the present invention is 150,000 to 20 million. When the mass average molecular weight is 150,000 or more, the effect of improving the moldability is excellent. Moreover, if a mass mean molecular weight is 20 million or less, the dispersibility in a styrene-type elastomer will become favorable.
The mass average molecular weight of the alkyl (meth) acrylate polymer is preferably 500,000 or more, more preferably 1,000,000 or more, and further preferably 1,600,000 or more. The mass average molecular weight of the alkyl (meth) acrylate polymer is preferably 15 million or less, more preferably 7 million or less.

  The mass average particle diameter in the latex of the alkyl (meth) acrylate polymer of the present invention is preferably 50 to 250 nm. If the mass average particle diameter is 50 nm or more, the influence of the emulsifier used in the emulsion polymerization on the styrene elastomer can be minimized. Moreover, if the mass average particle diameter is 250 nm or less, the termination reaction during the polymerization of the alkyl (meth) acrylate polymer is unlikely to occur, and it is easy to obtain a molecular weight having a mass average molecular weight of 1.6 million or more.

The processing aid for styrene elastomer of the present invention contains the alkyl (meth) acrylate polymer of the present invention.
The processing aid for styrene-based elastomer may contain one kind of alkyl (meth) acrylate polymer, or may contain two or more kinds different in molecular weight, composition, particle diameter and the like.
In addition to alkyl (meth) acrylate polymers, styrene elastomer processing aids are lubricants, light stabilizers, UV absorbers, oxidation agents, as long as they do not impair the properties of styrene elastomer processing aids. You may contain various additives, such as an inhibitor and a flame retardant.

The styrene elastomer used in the present invention is not particularly limited, but in terms of flexibility, rubber elasticity, and high temperature fluidity, styrene-butadiene-styrene block type, styrene-isoprene-styrene block type, styrene-ethylene-butylene-styrene. At least one selected from block types is preferred.
Among these, a hydrogenated styrene-ethylene-butylene-styrene block type (hereinafter referred to as “hydrogenated SEBS”) is particularly preferable.

As the hydrogenated SEBS, for example, product names “Tuftec H1031”, “H1041”, “H1043”, “H1051”, “H1052”, “H1053”, “H1062”, “1141”, Examples thereof include “same 1221”, “same 1272” (manufactured by Asahi Kasei Chemicals Corporation), and trade names “Dynalon 8601P”, “same 9901P” (manufactured by JSR Corporation).
These hydrogenated SEBSs may be used alone or in combination of two or more.

The styrenic elastomer composition of the present invention contains a styrenic elastomer processing aid and a styrenic elastomer.
The styrene elastomer composition preferably contains 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass of the processing aid for styrene elastomer with respect to 100 parts by mass of the styrene elastomer.
If the content of the processing aid for styrene elastomer relative to 100 parts by mass of the styrene elastomer is 0.5 parts by mass or more, the effect of improving the molding processability with respect to the styrene elastomer is sufficiently exhibited. Moreover, if content of the processing aid for styrene-type elastomers with respect to 100 mass parts of styrene-type elastomers is 20 mass parts or less, the characteristic which a styrene-type elastomer has will not be impaired.

The styrenic elastomer composition of the present invention may contain a reinforcing agent, a hygroscopic agent, a plasticizer, an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a mold release agent, a flame retardant, an antistatic agent, a dye as necessary. Known additives such as pigments, antifungal agents, antibacterial agents and inorganic fillers can be added.
In addition, polymers other than the above, such as natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, acrylic rubber, ethylene-α-olefin copolymer, ethylene-α-olefin-nonconjugated Diene copolymers, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene and the like can also be blended.

The styrenic elastomer composition of the present invention is blended with a processing aid for styrenic elastomer, a styrene elastomer, and various additives and other polymers as required, and then by a known method such as extrusion kneading or roll kneading. It is prepared by melt-kneading.
Further, a multi-stage blending is possible in which a master batch is prepared by mixing a part of the styrene elastomer processing aid and the styrene elastomer, and then the remaining styrene elastomer is blended.

Styrenic elastomer compositions have improved melt tension during molding, so the molten resin draw-down in vacuum molding or blow molding, cell foaming in foam molding, and take-off properties in calendar molding are improved. Further, molding processability such as blow molding, foam molding and calendar molding is improved.
Moreover, the discharge amount in extrusion molding, the surface appearance of the extrusion molded body such as a sheet and a film are improved, and the molding processability of the extrusion molding is also improved.

  The molded product of the present invention is obtained by molding the styrene elastomer composition of the present invention by a known method. Examples of the molding method include calendar molding, thermoforming, extrusion molding, extrusion blow molding, injection molding, and foam molding. As a molded object of this invention, the sheet | seat, film, and profile molded object by extrusion molding, the hollow molded object by injection blow molding or injection molding, an injection molded object, and a foaming molded object are mentioned, for example.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples. “Parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively.
Moreover, various physical properties in each example and comparative example are measured by the following methods (1) to (5).

(1) Mass average molecular weight The mass average molecular weight of the alkyl (meth) acrylate polymer is gel permeation chromatography (HLC-8220: Tosoh Corporation) using the tetrahydrofuran-soluble content of the alkyl (meth) acrylate polymer as a sample. )), A column (TSK-GEL SUPER HZM-M: manufactured by Tosoh Corporation).
The mass average molecular weight in the present invention was determined from a calibration curve using standard polystyrene.

(2) Mass average particle diameter A sample obtained by diluting latex with deionized water was measured using a particle size distribution meter (CHDF2000 type: manufactured by MATEC).
The measurement conditions were standard conditions recommended by MATEC. That is, using a special particle separation capillary type cartridge and carrier liquid, the liquidity: almost neutral, the flow rate: 1.4 ml / min, the pressure: about 4000 psi (2600 KPa), and the temperature: 35 ° C. 0.1 ml of the sample diluted to a concentration of about 3% was used for the measurement.
As the standard particle size substance, a total of 12 monodisperse polystyrenes with known particle sizes were used in the range of 20 to 800 nm.

(3) Handling as powder The processing aid was passed through an 8-mesh sieve. The handleability as a powder was evaluated according to the following criteria.
○: The amount that passed through the mesh is 90% or more △: The amount that passed through the mesh is 50% or more and less than 90% ×: The amount that passed through the mesh is less than 50%

(4) Melt tension Melt tension was evaluated as an index of moldability. Melt tension is an indicator of thermoformability, blow moldability, foam moldability, and the like, and an improvement in melt tension can be regarded as an improvement in moldability.
The melt tension was measured as follows.
The styrene elastomer, a capillary rheometer (Twin capillary rheometer RH-7: Rosand Inc.) was used to extrude a constant weight (0.54 cm ³ / min), taken off the strand at a constant speed (6 m / min) It was. The L / D of the die was 16.0 mm × φ1.0 mm, and the temperature was 190 ° C.
The improvement effect of melt tension was evaluated according to the following criteria.
○: 1.5 times or more with respect to the blank △: 1.2 times or more with respect to the blank and less than 1.5 times ×: less than 1.2 times with respect to the blank

(Production Example 1) Production of alkyl (meth) acrylate polymer (1) In a separable flask equipped with a thermometer, a nitrogen introduction tube, a cooling tube and a stirrer, 100 parts of isobutyl methacrylate, sodium dodecylbenzenesulfonate 1. 1 part and 300 parts of deionized water were added, and the inside of the container was replaced with nitrogen. Next, the internal temperature was raised to 60 ° C., and 0.15 part of potassium persulfate was added. Thereafter, heating and stirring were continued at 60 ° C. for 2 hours to complete the polymerization, and a latex of the alkyl (meth) acrylate polymer (1) was obtained.
The latex of the obtained alkyl (meth) acrylate polymer (1) was dropped into 100 parts of hot water containing 5 parts of calcium acetate to coagulate the latex.
The coagulated product was separated and washed and then dried at 65 ° C. for 16 hours to obtain an alkyl (meth) acrylate polymer (1).

(Production Examples 2 to 5) Production of alkyl (meth) acrylate polymers (2) to (5) Alkyl (meta) was prepared in the same manner as in Production Example 1 except that the charged composition was changed to the ratio shown in Table 1. ) Acrylate polymers (2) to (5) were obtained.

(Production Example 6) Production of alkyl (meth) acrylate polymer (6) The following monomer mixture was stirred at 10,000 rpm for 6 minutes using a homomixer and then forcedly emulsified using a homogenizer at a pressure of 200 kg / cm. Thus, an emulsified mixture was obtained.
Monomer mixture:
2-ethylhexyl methacrylate 100 parts sodium dodecylbenzenesulfonate 1 part deionized water 300 parts

The above emulsified mixture was put into a separable flask equipped with a thermometer, a nitrogen introducing tube, a cooling tube, and a stirring device, and the inside of the container was replaced with nitrogen. Next, the internal temperature was raised to 60 ° C., and the following reducing agent aqueous solution was added.
Reducing agent aqueous solution:
Ferrous sulfate 0.0003 parts Ethylenediaminetetraacetic acid disodium salt 0.0009 parts Rongalite 0.1 part Deionized water 5 parts Subsequently, 0.15 part of t-butyl hydroperoxide was added.
Then, heating and stirring were continued for 2 hours to complete the polymerization, and an alkyl (meth) acrylate polymer (6) latex was obtained. Subsequent operations were carried out in the same manner as in Production Example 1 to obtain an alkyl (meth) acrylate polymer (6).

(Production Examples 7 and 8) Production of alkyl (meth) acrylate polymers (7) and (8) Alkyl (meta) was obtained in the same manner as in Production Example 1 except that the charged composition was changed to the ratio shown in Table 1. ) Acrylate polymers (7) and (8) were obtained.

(Production Example 9) Production of alkyl (meth) acrylate polymer (9) Alkyl (meth) acrylate in the same manner as in Production Example 6 except that 2 parts of n-octyl mercaptan was added to the monomer mixture. A polymer (9) was obtained.

(Examples 1-6, Comparative Examples 1-3)
The obtained alkyl (meth) acrylate polymers (1) to (9) were used as processing aids (A-1) to (A-9) for styrene elastomers.
The handleability as a powder of the processing aids (A-1) to (A-9) for styrene elastomer was evaluated. The evaluation results are shown in Table 1.

表中の略号は下記の通り。
ｉＢＭＡ ：イソブチルメタクリレート
ｎＢＭＡ ：ｎ−ブチルメタクリレート
２ＥＨＭＡ ：２−エチルヘキシルメタクリレート
ＭＭＡ ：メチルメタクリレート
ｎＢＡ ：ｎ−ブチルアクリレート
連鎖移動剤 ：ｎ−オクチルメルカプタン

Abbreviations in the table are as follows.
iBMA: isobutyl methacrylate nBMA: n-butyl methacrylate 2EHMA: 2-ethylhexyl methacrylate MMA: methyl methacrylate nBA: n-butyl acrylate chain transfer agent: n-octyl mercaptan

(Examples 7-12, Comparative Examples 4-6)
As the styrene-based elastomer, Tuftec H1062 (trade name, manufactured by Asahi Kasei Chemicals Corporation) was used and blended with the processing aids for styrene-based elastomers (A-1) to (A-8) in the proportions shown in Table 2.
Thereafter, using a single screw extruder (manufactured by Thermoplastics Co., Ltd.), melt kneading was performed at a barrel temperature of 190 ° C. and a screw rotation number of 35 rpm to obtain a styrene elastomer composition. For Comparative Example 6, the same operation was performed without blending the processing aid for styrene elastomer.
Table 2 shows the melt tension of the obtained styrene-based elastomer composition.

  As is clear from Table 1, the processing aids for styrene elastomers of Examples 1 to 6 and Comparative Examples 1 and 2 were good in handling as powders, but the processing for styrene elastomers of Comparative Example 3 was good. The auxiliary agent was found to be poor in handling as a powder.

As is apparent from Table 2, the styrene elastomer compositions of Examples 7 to 12 containing the styrene elastomer processing aid of the present invention were compared with Comparative Example 6 where no styrene elastomer processing aid was blended. In comparison, an improvement in melt tension was observed.
On the other hand, in the styrene elastomer composition of Comparative Example 4, the mass average molecular weight of the processing aid for styrene elastomer was outside the range of the present invention, and the effect of improving the melt tension was not recognized.
In the styrene elastomer composition of Comparative Example 5, the composition of the processing aid for styrene elastomer is outside the scope of the present invention, the compatibility with the styrene elastomer is low, and strand breakage occurs during extrusion. Abandoned the measurement.

  As described above, from Tables 1 and 2, it was confirmed that the processing aid for styrene-based elastomer of the present invention is excellent in powder handleability and excellent in the effect of improving melt tension. Therefore, it can be seen that the processing aid for styrene-based elastomer of the present invention is extremely useful industrially.

The processing aid for styrene elastomer of the present invention has good dispersibility in the styrene elastomer, and can improve the molding processability of the styrene elastomer.
To provide a styrene-based elastomer composition excellent in take-up property at the time of calender molding, thermal formation, blow moldability, foam moldability, etc. by blending the processing aid for styrene-based elastomer of the present invention with the styrene-based elastomer. Can do. In addition, the styrenic elastomer composition of the present invention is improved in the surface condition of an extrusion-molded product such as a sheet and a film, and has good extrudability.
The styrenic elastomer composition obtained by the present invention can be used for various applications. Specifically, food-related applications such as food containers and food packaging, daily miscellaneous goods, toys and exercise equipment applications, stationery applications, automotive interior and exterior applications, civil engineering and construction applications, household appliances applications, clothing and footwear applications, medical applications It can be used for sanitary goods, packaging transportation materials, electric wire applications, etc.

Claims (4)

  A processing aid for styrenic elastomers containing an alkyl (meth) acrylate polymer having an alkyl (meth) acrylate unit having 2 or more carbon atoms in the alkyl group as a main component and a weight average molecular weight of 150,000 to 20 million. .   The processing aid for styrenic elastomers according to claim 1, comprising an alkyl (meth) acrylate unit having 2 to 6 carbon atoms in the alkyl group as a main component.   A styrenic elastomer composition comprising the processing aid for styrenic elastomer according to claim 1 or 2 and a styrenic elastomer.   The molded object obtained by shape | molding the styrene-type elastomer composition of Claim 3.