JPH05279484A - Composition for powder molding - Google Patents

Abstract

PURPOSE:To obtain the subject composition, comprising a specific amount of an aromatic vinyl compound monomer unit as a polymer molecular structural unit, having a specified number-average molecular weight, rich in soft feeling, good in molding processability such as powder fluidity and useful as automotive skin materials, etc. CONSTITUTION:The objective composition for powder molding, rich in soft feeling, good in molding processability without causing stickiness, fogging, etc., of moldings and composed of particles having a prescribed average particle diameter is obtained by polymerizing an aromatic vinyl compound such as styrene and butadiene according to a living polymerization method, providing an aromatic vinyl compound-butadiene block copolymer, containing 20-50wt.% aromatic vinyl compound monomer unit and having 20000-50000 number-average molecular weight, subjecting the resultant copolymer to hydrogenating treatment, affording a hydrogenated aromatic vinyl compoundbutadiene block copolymer, then blending the hydrogenated block copolymer with magnesium stearate, an ultraviolet light absorber, an antioxidant, a pigment, etc., thermally mixing the prepared blend in an extruder, extruding the mixture, pelletizing the extrudate and treating the obtained pellets in a turbomill type pulverizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a block copolymer composition composed of an aromatic vinyl compound for powder molding, ethylene and butylene, which is suitable for skin materials for automobile interiors and the like.

[0002]

2. Description of the Related Art Recent demands for skin materials for automobile interiors such as crash pads, console boxes, headrests, armrests, etc. are to provide lightweight and soft feeling, and to give a high-class feeling with leather pattern or stitch pattern. There is also a need for deep undercuts in the design, and it is essential to satisfy not only the conventional requirements for physical properties, but also the sensory requirements such as touch and design characteristics. .. The materials conventionally used for these skin materials are soft PVC and AB.
S resin or paste PVC or the like, and vacuum forming, sol slush molding, sol rotational molding or the like has been mainly used as a molding method. However, the skin material formed by vacuum molding using a soft PVC resin or ABS resin is
Although it is possible to reduce the weight, not only can the molded product have a hard feel, but it does not become a high-grade product due to flow restriction and stitch pattern flow during vacuum forming, and there is deep drawing and undercut. It had the drawback of being difficult to mold. Also, the sol molded product made of paste PVC resin is
Although a soft feel and a high-grade feel can be achieved, there is a drawback that the tendency of thickening is unavoidable due to the high sol viscosity, it is difficult to maintain the thickness uniformity, and it is impossible to achieve the weight reduction. Further, it takes a long time to discharge the sol from the mold at the time of molding, and it takes a long time to clean the tank, the pipe, etc. at the time of color change, which causes a serious problem in productivity. In order to solve these problems, so-called powder molding methods such as powder slush molding, fluidized-bed molding, and powder rotational molding have recently attracted attention, and powder slush molding is particularly used for molding skin materials for automobile interiors. Molding has come to be widely used. The powder material composition to be subjected to such powder molding must have excellent powder fluidity and moldability due to the characteristics of the molding process. By the way, most of the compositions used for powder slush molding of skin materials for automobile interiors are vinyl chloride-based compositions at present,
The skin-molded product obtained from these compositions has a better feel, gloss and design than the skin-molded product obtained by vacuum molding. However, in recent years, there has been a demand for a higher-grade skin material for automobile interiors, which has a good feel and a soft feel, rather than that obtained by powder slush molding of vinyl chloride. Attempts have been made to add a larger amount of plasticizer than before to obtain a soft feeling. However, when a large amount of a plasticizer is added to a vinyl chloride resin, the softness of the molded product is improved, but the stickiness of the plasticizer is generated and inconveniences such as fogging occur. In addition, when the plasticizer is added to the limit of the plasticizer absorption capacity of the vinyl chloride resin, a large amount of the plasticizer is leached on the surface of the vinyl chloride resin particles and the adhesiveness thereof deteriorates the powder fluidity. There is a defect in moldability that an accurate thickness in a thin-walled molded product required for a skin molding material cannot be obtained.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention has a soft feeling, does not cause stickiness, fogging, etc. of a molded product which is a drawback caused by a plasticizer, and has powder flowability and the like. It is an object of the present invention to provide a powder molding composition having good molding processability.

[0004]

SUMMARY OF THE INVENTION In view of the drawbacks caused by the addition of a plasticizer in the prior art, the inventors of the present invention did not achieve a soft feeling by a method other than the addition of a plasticizer, and as a result of earnest research. Hydrogenated styrene-butadiene block copolymer has a good soft feeling without a plasticizer if a proper molecular weight range is selected, and it is free from stickiness due to the plasticizer and powder molding. Therefore, the present invention has been completed based on this finding. That is, the present invention has an aromatic vinyl compound monomer unit of 20 to 50% by weight as a polymer molecular constitution unit, and an aromatic vinyl compound-butadiene block copolymer having a number average molecular weight of 20,000 to 50,000. The present invention provides a powder molding composition containing a hydride of a polymer.

The hydride of the aromatic vinyl compound-butadiene block copolymer used in the present invention is one in which the double bond portion of the butadiene chain unit is saturated by the hydrogenation treatment, and the hydrogenated butadiene monomer The butadiene monomer unit is composed of two ethylene monomer units or one butene group having an ethyl group side chain depending on whether the bonding mode in the polymer is 1,4 bond or 1,2 bond. It becomes one monomer unit. Therefore, when the hydride of the aromatic vinyl compound and the butadiene block copolymer is viewed from the viewpoint of the polymer molecular structure after the hydrogenation treatment, the chain block of the aromatic vinyl compound monomer unit and the ethylene monomer unit are It is a block copolymer composed of a copolymerization chain block composed of and a butene-1 monomer unit. Hereinafter, a copolymer of this type which is used in the present invention is referred to as a hydride of the present invention.

The block structure of the hydride of the present invention is a linear or branched block polymer having one or more aromatic vinyl compound blocks and one or more hydrogenated butadiene chain unit blocks in one molecule of the polymer. As the linear structure, S-B type, S-B-S type, B-S-B
Block copolymers such as mould, S-B-S-B type can be used. Here, S is an aromatic vinyl compound block chain, and B is a hydrogenated butadiene unit butadiene chain. These block copolymers can be easily produced by a known living polymerization method using, for example, a butyllithium catalyst. As the aromatic vinyl compound used in the hydride of the present invention, for example, styrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, t-butylstyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, etc. may be used. it can.

The hydride of the present invention has an aromatic vinyl compound unit content of 10 to 50% by weight, preferably 20 to 4%.
0% by weight, the content of hydrogenated butadiene units is 90 to 50% by weight, preferably 80 to 60% by weight. When the aromatic vinyl compound content is less than 10% by weight, the aromatic vinyl compound block chain is inevitably reduced, the fluidity becomes too large, and melt drip occurs during molding,
There is the inconvenience of causing blocking during storage. Also,
When the content of the aromatic vinyl compound exceeds 50% by weight, the molding temperature becomes too high, which lowers the productivity, increases the hardness of the molded product, lowers the soft feel, and deteriorates the feel. The hydride of the present invention has a number average molecular weight of 20,000 to 50,000.
It is necessary to use 0, preferably 30,000 to 40,000.

When the number average molecular weight is less than 20,000, the fluidity becomes large, resulting in melt drip during molding and blocking during storage. Further, if the number average molecular weight exceeds 50,000, good sinterability cannot be obtained, so that the powder molding method cannot be applied. There are 1,2 bonds and 1,4 bonds in the bonding system of the butadiene unit before hydrogenation in the block chain of the hydrogenated butadiene unit in the hydride of the present invention, but the ratio of these has little influence on the present invention. The hydride of the present invention, to the extent that does not impair the soft feeling and powder moldability which is the object of the present invention,
Other monomer units can be used as a structural unit of the chain block for the purpose of improving the adhesion with other materials. As the other monomer unit used here, the aromatic vinyl compound unit block chain, for example, a monomer such as α-methylstyrene, acrylonitrile, methyl methacrylate, methyl acrylate can be copolymerized, butadiene For the unit block chain, for example, monomers such as styrene, isoprene, and 1,3-pentadiene can be used. Further, in order to introduce an epoxy group or a polar group having active hydrogen, a monomer containing an epoxy group, a carboxylic acid group, a hydroxyl group or the like, for example, glycidyl vinyl ether, acrylic acid is copolymerized or treated after the copolymerization. Then, by introducing an epoxy group or by generating a hydroxyl group or a carboxylic acid group by hydrolysis, the adhesiveness with other materials such as polyurethane foam can be improved.

The powder molding composition of the present invention may contain a small amount of another polymer, for example, vinyl chloride resin, polybutadiene, SBR, etc. within a range that does not impair the soft feeling and molding processability. The powder molding composition of the present invention includes
Various additives can be added as desired. For example, metal soaps such as barium stearate, calcium stearate, magnesium stearate, zinc stearate, and aluminum stearate, and fatty acid esters of polyhydric alcohols for improving mold release during molding and preventing blocking during storage. Can be added.
As other additives, various known stabilizers, antioxidants, UV inhibitors, antistatic agents, flame retardants, pigments and the like can be added. Further, known plasticizers can also be added within a range that does not impair the stickiness and moldability.

The powder molding composition of the present invention is a powdery composition obtained by appropriately mixing the above-mentioned components with the hydride of the present invention and heating and mixing the mixture with an extruder, a heating roll or the like. Can be used as a powder molding material. In the powder step in the production of the composition of the present invention, for example, a pulverizer such as a turbo mill, a roller mill, a ball mill, a centrifugal pulverizer, and a pulverizer can be used to make powder. The composition of the present invention has an average particle size of 50 to 500 μm, preferably 100 to 300 μm, depending on the pulverization process.
It is desirable to use it after crushing. Average particle size is 50 μm
If it is less than the above range, the efficiency of the pulverizing process is poor and, moreover, it tends to aggregate during storage. On the other hand, if it exceeds 500 μm, the texture of the molded product becomes rough and pinholes are easily generated in the case of a molded product having a small thickness. Therefore, it is desirable that the average particle diameter be 500 μm or less. The powder molding composition of the present invention can be used in various powder molding methods such as powder slush molding, fluid immersion molding, and powder rotational molding, and is particularly preferably used as a powder molding material for automobile interior skin materials. be able to.

[0011]

EXAMPLES The present invention will be described in more detail by way of examples. Using the powder molding compositions obtained by synthesizing hydrides A to J of styrene-butadiene block copolymers having styrene contents and number average molecular weights shown in Table 1 by a living polymerization method and using these The physical properties of the molded product were measured. The block copolymer before the hydrotreatment was an S-B-S type block copolymer, and the vinyl content of the B block chain was about 30%.

[0012]

[Table 1]

The amount of bound styrene in the hydride of the block copolymer was measured by NMR. All of the hydrogenated butadiene monomer units other than the amount of bound styrene shown in the hydrides A to J of the block copolymer. Further, the number average molecular weight was calculated from a molecular weight distribution curve measured using high performance liquid chromatography, based on a calibration curve previously obtained from the analysis results of standard polystyrene of known molecular weight. Preparation of test material 100 parts by weight of hydride of styrene-butadiene block copolymer shown in Table 1, 1.0 part by weight of magnesium stearate, 0.3 part by weight of hindered amine type ultraviolet absorber, hindered phenol type antioxidant 0.2 parts by weight of the agent and 1.0 parts by weight of the pigment were added, and the extruder (single screw type, φ6
5 mm) and heated and mixed at a head die temperature of 150 ° C. to prepare pellets having a diameter of about 3 mm and a length of about 5 mm. Further, the pellets were subjected to a turbo mill type pulverizer to prepare a powder molding material having a predetermined average particle diameter.

The powder-forming material thus obtained was put into an oil-heated slush molding machine with a width of 200 mm and a length of 75 mm.
A sheet was prepared by using a mold of a 0 mm half instrument panel. The mold used at this time was an electroformed mold made of nickel and having a diaphragm. The molding conditions are as follows: When the surface of the mold is heated to 240 ° C. by heating with oil, the above powder molding material is charged and left for 5 seconds, then the mold is inverted to remove excess powder, The polymer composition was left standing for 30 seconds to accelerate the melting of the polymer composition. after,
Cooling oil was flowed and left for another 60 seconds, and when the temperature of the molded product reached about 50 ° C., the circulation of cooling oil was stopped. The sheet thus formed was held at one end, peeled at a speed of about 200 mm / sec and an angle of about 60 degrees, and released from the mold, and the elongation of the molded product and the properties of the molded product at that time were evaluated. Table 2 shows the types of materials to be evaluated, the average particle size of the powder, and the evaluation results.

[0015]

[Table 2]

The plate thickness of the molded product used as the evaluation sample is 1 mm. The mark * in Table 2 was not measurable because the melted state was insufficient and a sintered sheet could not be produced. The properties of the molded product were judged by the following five-level evaluation method. ⊚: The aperture on the front surface is completely transferred, and the back surface is also in a completely melted state. Almost no melt flow occurred during molding. ◯: The squeeze on the front surface is completely transferred, and the back surface is in a place where melting is slightly insufficient, or a slight melt flow during molding is observed, but there is no problem in using the product. Δ: There are a few pinholes on the surface. Alternatively, a part of the back surface where the melting is insufficient, or a melt flow during molding is observed. It can be dealt with by slightly changing the molding conditions. X: Many pinholes are present on the surface. Alternatively, the sheet is not completely melted and the original physical properties are not expressed, or the sheet thickness is uneven due to excessive melting. XX: The sheet is not melted and remains in a powder state.

[0017]

Industrial Applicability The present invention provides a powder molding composition satisfying the soft feeling and moldability that are strictly required as a skin material for automobiles. Further, since the composition of the present invention does not use a plasticizer. It is useful for powder molding because it does not have a bad feeling such as stickiness and does not have a plasticizer and is excellent in powder molding processability and storage blocking prevention property.

Claims (1)

[Claims] 1. An aromatic vinyl compound-butadiene block copolymer having 20 to 50% by weight of an aromatic vinyl compound monomer unit as a polymer molecular constitution unit and having a number average molecular weight of 20,000 to 50,000. A powder molding composition containing a combined hydride.