JPH0329253B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a masterbatch for foam molding consisting of a carrier resin and a blowing agent.
An object of the present invention is to provide a masterbatch for foam molding useful for use in PS resin (hereinafter referred to as PS resin) and acrylonitrile-styrene-butadiene resin (hereinafter referred to as ABS resin). (Prior art) Generally, when adding a foaming agent to PS resin or ABS resin and molding it, a powdered foaming agent is added to the raw material resin at a ratio of 0.5 to 2.0% by weight of the resin. It is molded and processed. Another method is to use a so-called masterbatch for foam molding, which is prepared by kneading a blowing agent in a proportion of 5 to 30% by weight with a carrier resin such as polyolefin thermoplastic resin or ethylene vinyl acetate resin. (Problems to be Solved by the Invention) However, when the above-mentioned foaming agent powder is used for molding, the use of a powdered foaming agent causes the scattering of the powder to the surroundings and the failure of the foaming agent. This often causes uneven foaming due to uniform dispersion, and poor penetration of the material when it is fed into a molding machine. In addition, using a foam molding masterbatch that uses polyolefin thermoplastic resin or ethylene-vinyl acetate resin as a carrier resin,
When PS resin or ABS resin is foam-molded, a molded product with low mechanical properties (mechanical strength, impact strength, etc.) is obtained due to these carrier resins. In addition, even if you try to manufacture a masterbatch for foam molding by kneading a blowing agent into PS resin or ABS resin as a carrier resin, the processing temperature of the resin (200 to 230°C) and the foaming decomposition temperature of the blowing agent (e.g. Azodicarbon acid foaming agent; 150~
200℃, sodium bicarbonate inorganic blowing agent; 150~
200°C) are close to each other or overlap, making it impossible to produce a masterbatch for foam molding. (Means for Solving the Problems) The present invention solves the above problems, and as a result of intensive research to obtain a master batch for foam molding to obtain high quality and stable foamed PS molded products and foamed ABS molded products, The present invention was completed based on the finding that a masterbatch for foam molding that solved the above problems could be obtained by mixing and kneading a polystyrene-polybutadiene thermoplastic elastomer, low molecular weight polystyrene, and a blowing agent. That is, the present invention is a masterbatch for foam molding comprising a polystyrene-polybutadiene thermoplastic elastomer, low molecular weight polystyrene, and a foaming agent. To explain the present invention in detail, according to the inventor's detailed research, a polystyrene-polybutadiene thermoplastic elastomer and low molecular weight polystyrene are combined and used as a carrier resin for a masterbatch for foam molding for PS resin or ABS resin. In this case, it has been found that these master batches can be easily manufactured and excellent molded products can be obtained without any deterioration of the physical properties of the PS resin or ABS resin used for molding. The polystyrene-polybutadiene thermoplastic elastomer used as one component of the carrier resin in the present invention includes, for example, a thermoplastic elastomer consisting of a polystyrene block and a polybutadiene block, and a polystyrene block and a polybutadiene block having a radial or teleblock structure. A thermoplastic elastomer bonded in a shape. The proportion of the above-mentioned carrier resin used is usually 30 to 70% by weight, since the frictional heat in the kneading machine during the manufacturing process of the masterbatch for foam molding may decompose the foaming agent.
Preferably it is 50 to 60% by weight. The low-molecular-weight polystyrene used as another component of the carrier resin in the present invention is a low-molecular-weight styrenic thermoplastic resin, and its molecular weight is usually on the order of several hundred to several tens of thousands. The proportion used is usually 5 to 40% by weight, preferably 5 to 40% by weight, as too much will make it difficult to pelletize in an extruder, and too little will impair processability in a kneader.
It is 10-30% by weight. The blowing agent used in the present invention may be either an inorganic blowing agent (sodium bicarbonate, citric acid, etc.) or an organic blowing agent (N,N'-dinitropentamethylenetetramine, azodicarbonamide, etc.). If the proportion used is too high, the material will not be absorbed into the kneading machine during the manufacturing process of the master batch for foam molding, and the distribution of the resin and the master batch for foam molding in the final molded product will be poor, causing uneven foaming. becomes. If the proportion of the blowing agent used is too low, the cost will increase. For this purpose it is usually 5 to 40% by weight, preferably 20 to 30% by weight. The basic constituent components of the masterbatch for foam molding of the present invention are the above three components, but in addition, various conventionally known organic and inorganic pigments may be added as necessary.
By adding an appropriate amount, it is possible to make a coloring foam molding masterbatch suitable for various uses. The method for producing the masterbatch for foam molding of the present invention from the above-mentioned various constituent components can be carried out in accordance with conventionally known methods. For example, the masterbatch for foam molding of the present invention can be obtained by uniformly mixing the above-mentioned components using a high-speed mixer or the like, and kneading the mixture into pellets using an extruder. (Effects of the Invention) The masterbatch for foam molding of the present invention obtained as described above is easy to manufacture, and can be used to produce PS resin or ABS resin.
When the resin is foam-molded, the foaming agent is easily and uniformly dispersed in the resin, and a molded product with good mechanical properties can be obtained. The present invention will be specifically described below with reference to Examples and Comparative Examples. In addition, parts in the text are based on weight. Example 1 "Solprene T-475" (trademark) (polystyrene-polybutadiene thermoplastic elastomer) 60
20 parts of Hymer SB75 (trademark) (low molecular weight polystyrene) and 20 parts of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) were mixed in a 20 liter super mixer for 3 minutes, and then mixed in an extruder (30 mm
The mixture was extruded at φL/D=24, compression ratio 1:3, temperature 80 to 150°C, and rotation speed 60 rpm) to form cylindrical pellets with a diameter of 2.0 to 3.0 mm. The pellets thus obtained had a smooth surface, and no coarse particles of the blowing agent were observed with the naked eye. 5 parts of the foam molding masterbatch obtained here and 100 parts of PS resin (50 parts of Styron 470 and 50 parts of Stylon 666) were mixed for 1 minute in a super mixer, and A molded product was obtained which was processed at a pressure of 80 Kg/cm ² , a secondary pressure of 50 Kg/cm ² , a back pressure of 0 Kg/cm ² , and cooling for 40 seconds. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Example 2 5 parts of the foam molding masterbatch obtained in Example 1 and 100 parts of ABS resin (Denka QF) were mixed in the same manner as in Example 1, and injection molded to obtain a molded product. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Example 3 "Solprene T-414" (trademark) (polystyrene-polybutadiene thermoplastic elastomer) 70
parts, 10 parts of "Himer SBM73F" (trademark) (low molecular weight polystyrene) and Uniform AZH25 (trademark)
20 parts of (asodicarbonamide, organic blowing agent) were extruded using an extruder in the same manner as in Example 1.
It was granulated into 3.0 mm cylindrical pellets. The pellets thus obtained were as good as in Example 1. 5 parts of the obtained foam molding masterbatch and 100 parts of PS resin were injection molded in the same manner as in Example 1 to obtain a molded product. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Example 4 5 parts of the foam molding masterbatch obtained in Example 3 and 100 parts of ABS resin (Denka QF) were injection molded in the same manner as in Example 3 to obtain a molded product. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Example 5 50 parts of "Tuffprene A" (trademark) (polystyrene-polybutadiene thermoplastic elastomer), "Himer ST95" (trademark) (low molecular weight polystyrene)
20 parts and 30 parts of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) were extruded using an extruder in the same manner as in Example 1, and granulated into cylindrical pellets with a diameter of 2.0 to 3.0 mm. The pellets thus obtained were as good as in Example 1. Masterbatch 3.3 for foam molding obtained here
and 100 parts of PS resin (50 parts of Stylon 470 and 50 parts of Stylon 666) were injection molded in the same manner as in Example 1 to obtain a molded product. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Example 6 3.3 parts of the foam molding masterbatch obtained in Example 5 and 100 parts of ABS resin (Denka QF) were injection molded in the same manner as in Example 5 to obtain a molded product. The mechanical properties and foaming state of the molded product thus obtained were good. The results are shown in Table 1. Comparative Example 1 1 part of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) and 100 parts of the PS resin used in the example were mixed for 1 minute in a 20 liter super mixer, and injection molded in the same manner as in the example. A molded product was obtained. Regarding the foamed state of the molded product thus obtained, uneven foaming was observed between the first molded product and the last molded product due to separation of the resin and the foaming agent. In addition, coarse particles of the blowing agent were also observed in some places on the surface of the molded product. The results are shown in Table 1. Comparative Example 2 A molded article was obtained using ABS resin in the same manner as in Comparative Example 1, but the results were similar to those in Comparative Example 1. Results first
Shown in the table. Comparative example 3 Suntec F2270 (low density polyethylene,
0.92MFR7) and 20 parts of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) were mixed for 3 minutes in a 20 liter super mixer, and granulated into cylindrical pellets in the same manner as in the example. A molded product was obtained by injection molding 5 parts of the obtained masterbatch for foam molding and 100 parts of PS resin in the same manner as in the example, but some layer peeling was observed on the surface of the molded product, and furthermore, the mechanical properties were poor. As shown in the table, both impact and strength are extremely reduced compared to Examples. The results are shown in Table 2. Comparative Example 4 The foam molding masterbatch obtained in Comparative Example 3 was similarly injection molded using ABS resin to obtain a molded product, but the results were similar to those in Comparative Example 3. The results are shown in Table 1. Comparative example 5 Styron 470 (PS resin) 80 parts and inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) 20 parts
An attempt was made to granulate the sample using the same procedure as in the example (however, the temperature was 180°C), but the blowing agent decomposed and granulation was impossible. Comparative Example 6 An attempt was made to granulate 80 parts of Solprene T-475 and 20 parts of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) in the same manner as in the example, but the extruder Hotsuparo was unable to bite into the material. Unfortunately, granulation was impossible due to foaming of the pellets. Comparative Example 7 An attempt was made to granulate 80 parts of Hymer SB75 and 20 parts of an inorganic blowing agent (sodium bicarbonate/citric acid blowing agent) in the same manner as in the Examples, but the results were similar to those in Comparative Example 6.

[Table] 2 4 6 2 4

ABS resin 10 9 9 9
7

[Table] Comparative example 2 Comparative example 4

Claims (1)

[Claims] 1 A masterbatch for foam molding comprising a polystyrene-polybutadiene thermoplastic elastomer, low molecular weight polystyrene, and a foaming agent.