JPS6324012B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a glass fiber-reinforced polyolefin sheet for press molding to obtain molded products with excellent physical properties, particularly strength, rigidity, impact resistance, heat resistance, and color tone. Generally, polyolefins are molding materials with excellent physical and chemical properties, but many attempts have been made to make them even better by further reinforcing them with glass fibers. The manufacturing method is to add glass fiber to polyolefin,
The mixture is melt-kneaded using a screw extruder, Banbury mixer, roll, etc. to form a uniformly dispersed compound, and then molded using an injection molding machine, press molding machine, etc. When considered as a compound,
In order to improve the adhesion of polyolefins to glass fibers, the surface of the glass fibers is treated with a suitable silane coupling agent or the polyolefins are modified. In particular, the latter method has a large modification effect due to maleic anhydride,
The method is shown in USP3416990, Japanese Patent Publication No. 43-27421, etc. However, the glass fibers contained in molded articles obtained using these compounds are cut during the compounding process, that is, during melt-kneading, and the reinforcing effect is significantly reduced. In particular, the drop in impact resistance is significant and it cannot be used as a structural material. Recently, in order to improve these points, a method has been developed to obtain molded products using a press molding method from sheets made of laminated mats made of thermoplastic resin and long glass fibers. As a high-performance material, it is introduced, for example, in Japanese Patent Application Laid-Open No. 52-40588 and Japanese Patent Application Laid-Open No. 48-80172.
According to these, a mat made of a thermoplastic resin and long glass fibers is laminated or a mat made of long glass fibers is impregnated with a thermoplastic resin to temporarily form a glass fiber-reinforced thermoplastic resin sheet, and then the sheet is used as a molded product. After cutting it into a size suitable for the size, heating it by infrared heating means to a temperature higher than the melting point or softening point of the thermoplastic resin that is the matrix component,
Next, this is transferred to a press mold such as a mated die that has been cooled to below the melting point or softening point of the thermoplastic resin, and press molding is performed to obtain a molded product. However, it has been found that various problems occur when this method is applied to polyolefins. That is, simply combining polyolefins and long glass fiber mat does not provide a sufficient reinforcing effect even though it contains long glass fibers because the adhesion between the glass fibers and the polyolefin is poor. When a modified polyolefin containing 0.14 to 4.5% by weight of maleic anhydride as disclosed in USP 3,416,990 is used as a method for increasing the adhesive effect, the sheet undergoes severe thermal discoloration during heating prior to press molding, resulting in poor yield. It was found that the molded product was discolored to yellowish brown, and its heat aging resistance was significantly reduced. In view of the above, the present inventors conducted intensive research to obtain a glass fiber-reinforced polyolefin sheet for press molding to obtain molded products with excellent strength, rigidity, impact resistance, heat resistance, and color tone. Modified polyolefin or a mixture of modified and unmodified polyolefin with an acid content in the range of 0.003 to 0.1% by weight and a major length of 1 cm.
It is a sheet-shaped composite made of the above glass fibers, and the sheet is characterized by expanding in the thickness direction of the sheet and becoming porous when heated above the melting point or softening point of the polyolefin. The present inventors have discovered that a molded article that successfully overcomes the above-mentioned drawbacks can be obtained by using a glass fiber reinforced polyolefin sheet for press molding, and have thus completed the present invention. That is, the present invention relates to a glass fiber-reinforced polyolefin sheet for press molding to obtain a molded product having excellent strength, rigidity, impact resistance, heat resistance, and color tone. The present invention will be explained in detail below. Examples of the polyolefin used in the present invention include polyethylene, polypropylene, polystyrene, polymethylpentene-1, and copolymers or mixtures thereof.These include dyes and pigments, heat stabilizers, antioxidants, and ultraviolet absorbers. , plasticizers, fillers, etc. may be added. There are various reports on modification treatment methods for maleic anhydride, including a method of melt-kneading in the presence of organic peroxides and a solution method in which polyolefins are dissolved in a solvent. A simple method is to react maleic anhydride and polyolefins in the presence of an organic peroxide in an extruder. The fibers of the glass fiber mat used in the present invention have a diameter of 2 to 30 μm, preferably 5 to 25 μm, and a continuous length of 1 cm or more. These fibers are used as a bundle of several or more fibers. An important point in the present invention is that the sheet of glass fiber mat and modified polyolefin becomes porous upon heating. As a method for making it porous, the glass fiber mat is bulky and is under compression in the sheet, but once the polyolefin is heated above its melting point, the glass fiber mat is released from its compressed state. There are a method in which the sheet expands in the thickness direction of the sheet by restoring the bulkiness of the sheet to make it porous, and a method in which a foaming agent is used, but the former is preferred in the case of the present invention. Examples of such bulky pine include glass lawn continuous strand pine sold by Asahi Fiberglass Co., Ltd. and format sold by Fiberglass Industries, Inc. of the United States. The reason why these have bulkiness is not completely understood, but it is thought to be roughly as follows. Glasslon continuous strand mat has continuous long fibers deposited in an arc shape to form a bulky mat, and the continuous strands are bonded with a thermosetting binder. Therefore, it is thought that it was solidified into a pine-like shape while retaining some of its bulk when it was deposited, and even if it loses its bulk once it is put under compression, once it is released, it is almost the same as before. This is thought to restore the bulkiness of the material. On the other hand, format is a mat made by mechanically joining chopped strands of about 1 to 3 cm with a needle punch. They are oriented and intertwined. For this reason, pine is fluffy and bulky, and even if it is once compressed, it is thought that once it is released, it will regain its original bulk due to the glass strands oriented in the thickness direction. However, it should be noted that not all needle punched materials exhibit bulk. For example, if the mat weight is 200 g/m ² or more according to those in the industry, it will show bulkiness depending on the needle punching conditions, but if it is less than that, it will not show much bulkiness. This is thought to be due to the fact that when the mat weight is small, the mat thickness is small, and once the glass strands oriented in the thickness direction are compressed, their orientation is easily changed in the in-plane direction. In the present invention, a mat weight of 200 g/m ² , preferably 300 g/m ² or more should be selected in order to obtain the bulkiness due to needle punching. Various other glass fiber pine structures that can regain bulkiness are conceivable, but the important point in the present invention is not the method by which the glass fiber pine structure can regain bulkiness, but rather the method by which a sheet made of polyolefin resin and glass fiber pine is used. When the polyolefin resin is heated above its melting point, it expands in the thickness direction and becomes porous. The present inventors have discovered that a molded product obtained by press-molding a glass fiber-reinforced polyolefin sheet made of such bulky glass fiber mat and modified polyolefin after heating it above the melting point of the modified polyolefin has excellent properties. I found it. Conventionally, maleic anhydride modification has been widely used to improve the adhesion between polyolefins and glass fibers, but the amount of reacted maleic anhydride required in that case is compared with the previously known amount. It should be extremely small, that is, 0.003~
It has been found that excellent properties can be obtained within the range of the amount of reacted maleic anhydride of 0.1% by weight. The reason for this is not completely understood, but it is thought to be roughly as follows. The maleic anhydride-modified polyolefin, which is the matrix of the sheet, is heated above its melting point to expand and become porous. In the sheet, the modified polyolefin impregnated into the glass fiber mat is formed into three-dimensionally entangled glass. Among the fibers or strands, some are in the form of lumps, while others are in the form of a film. As a result, the surface area of the modified polyolefin that comes into contact with air is very large, and since it is exposed to high temperatures, it is thought that the modified polyolefin is activated by oxygen in the air. Due to the synergistic effect of this effect and the adhesion-improving effect of maleic anhydride, the adhesive force between the modified polyolefin and glass fibers becomes sufficiently large despite the extremely low amount of reactive maleic anhydride in the polyolefin. It is thought that there are. If the amount of reacted maleic anhydride in the polyolefin is 0.1% by weight or more, the modified polyolefin that is the matrix will change color during heating of the sheet, and the color tone of the obtained molded product will not only be inferior, but also Heat aging resistance becomes extremely poor.
If the amount of reacted maleic anhydride is less than 0.003% by weight, the adhesion between the glass fiber and polyolefin will be poor and sufficient strength will not be obtained. The degree of expansion necessary for the heating sheet to become porous is 1.5 to 5 times the thickness of the sheet when unheated. Expanding five times or more has no effect on improving the adhesive strength between the glass fiber and polyolefin, but the surface properties of the molded product deteriorate. The method of lamination and impregnation is also important in order for the sheet to expand in the thickness direction and become porous. Naturally, when the surface layer of the sheet is a thick resin layer, it is less likely to become porous, and the preferable thickness of the surface resin layer is 1.2 mm or more and preferably 0.9 mm or less. The surface of the glass fiber used in the present invention can be treated with a sizing agent such as a binder, lubricant, emulsifier, PH regulator, antistatic agent, coupling agent, etc. in the form of a single fiber, strand, or mat. The sheet according to the present invention is obtained by laminating and impregnating a modified polyolefin containing reactive maleic anhydride in an amount of 0.003 to 0.1% by weight and a bulky glass fiber mat, most of which is 1 cm or more in length, using an extruder or press. obtained by. The amount of glass fibers contained in the sheet can be selected as appropriate, but is usually 5 to 80% by weight, preferably 10 to 60% by weight. The glass fiber reinforced polyolefin sheet is then cut according to the size of the molded product to be obtained, and heated by means such as infrared rays to a temperature above the melting point or softening point and below the decomposition temperature of the modified polyolefin that is the matrix of the sheet. The modified polyolefin is then transferred to a press mold such as a mated metal die that has been cooled to a temperature below the melting point or softening point of the modified polyolefin, and the mold is closed to perform press molding. The molded product obtained by the present invention has good strength, rigidity, impact resistance, fatigue resistance, and heat aging resistance because the glass fiber is a long fiber and the adhesive force between the glass fiber and polyolefin is strong. Excellent color and good color tone. In order to make the present invention even clearer, the following describes
Examples are also given without limiting the scope of the invention. Example 1 4000g of powdered isotactic polypropylene (Sumitomo Noblen S101 manufactured by Sumitomo Chemical)
, 4 g of maleic anhydride and 2 g of benzoyl peroxide.
was dissolved in 80 g of acetone and added, mixed in a Henschel mixer, melted and kneaded in a nitrogen-sealed extruder, and extruded into sheets with thicknesses of 0.7 mm and 2 mm. The reaction amount of maleic anhydride determined by infrared spectrum was 0.09% based on polypropylene. For the glass fiber mat, glass fiber roving (#712/66 manufactured by PPG, USA) was cut into approximately 3 cm pieces using a chipped strand cutter, and then the pieces were randomly oriented and piled up, then needle punched to give a total weight of 900 g/ A bulky pine of m ² was obtained.
Needle punching conditions are needle size 25,
The needle density was 100 times/cm ² and the needle depth was 20 mm. Next, modified polypropylene sheet 0.7 mm/glass fiber mat (900 g/m ² )/modified polypropylene sheet 2 mm/glass fiber mat (900 g/m 2 )
They were laminated so that m ² /modified polypropylene sheet was 0.7 mm, and pressed to obtain a reinforced polypropylene sheet (GF content: 40% by weight). The thickness of the sheet is
It was 3.8mm. Next, the sheet was heated to about 210°C in an infrared oven, and then held under a pressure of 30 kg/cm ² for 20 seconds in a matte metal die controlled at 80°C to form a box-shaped molded product without discoloration. Obtained. A JIS No. 1 dumbbell test piece and an Izod impact test piece were cut out from the molded product, and a tensile strength of 1150 Kg/cm ² and an Izod impact value of 60 Kg-cm/cm were obtained. Further, as a result of accelerated heat aging test at 135°C, no decrease in tensile strength was observed even after 2000 hours. Note that the sheet according to this example expanded to about 2.4 times the thickness after heating with infrared rays, and was porous. Example 2 4000g of powdered isotactic polypropylene (Sumitomo Noblen S101 manufactured by Sumitomo Chemical)
, 4 g of maleic anhydride and 2 g of benzoyl peroxide.
was dissolved in 80 g of acetone and added, mixed in a Henschel mixer, melted and kneaded in an extruder sealed with nitrogen, and extruded into pellets. The obtained pellets and isotactic polypropylene (Sumitomo Noblen W501, manufactured by Sumitomo Chemical) were dry blended at a ratio of 1:15, and melt-kneaded using an extruder to a thickness of 0.7.
Sheets of mm and 2 mm were obtained. A molded article was obtained in the same manner as in Example 1 except that this sheet was used in place of the sheet in Example 1. The results are shown in Table 1. Example 3 High-density polyethylene (Asahi Kasei S360) was used instead of the isotactic polypropylene of Example 1.
A molded article was obtained in the same manner as in Example 1 except that a molded article was used. The results are shown in Table 1. Example 4 Instead of one sheet of glass fiber mat in Example 2,
Glasslon Container Strand Mat (Asahi Glass Fiber CSM8600; 450g/
A molded article was obtained in the same manner as in Example 2, except that two pieces of m ² ) were used. The results are shown in Table 1. Comparative Example 1 4000g of powdered isotactic polypropylene (Sumitomo Noblen S101 manufactured by Sumitomo Chemical)
6 g of maleic anhydride and 3.5 g of benzoyl peroxide.
g was dissolved in 120 g of acetone, mixed in a Henschel mixer, melt-kneaded in a nitrogen-sealed extruder, and extruded into sheets with thicknesses of 0.7 mm and 2 mm. The reaction amount of maleic anhydride determined by infrared spectrum is 0.15% based on polypropylene.
It was hot. A molded article was obtained in the same manner as in Example 1 except that the sheet was used. From the obtained molded product
A JISI dumbbell test piece and an Izot impact test piece were cut out, and the tensile strength/130 Kg/cm ² and Izot impact value 62 Kg-cm/cm were obtained, which were almost the same values as in Example 1, but the molded product did not turn yellow. The results of an accelerated chemotaxis test at 135°C showed that the tensile strength after 2000 hours had decreased to 60% of its initial value. Comparative Example 2 A molded article was obtained in the same manner as in Example 2, except that the ratio of modified polyolefin and unmodified polyolefin in Example 2 was changed to 1:40. Tensile strength is 800Kg/cm ² ,
The Izot impact strength was 45 Kg-cm/cm, which was lower than that of the present invention. Comparative Example 3 A modified polyolefin sheet having the same formulation as in Example 2 but having a thickness of 0.3 mm was obtained. As the glass fiber mat, glass fiber roving (#712/66 manufactured by PPG, USA) was cut into approximately 3 cm pieces using a chopped strand cutter, and then the pieces were randomly piled at a weight of 180 g/ ^m2 . The material was needle punched to obtain glass fiber mat. Needle punching conditions are implementation 1
It was the same. Next, the mat and the above modified polypropylene sheet with a thickness of 0.3 mm were stacked alternately,
A reinforced polypropylene sheet consisting of 10 layers of the glass fiber mat and 11 layers of modified polypropylene sheet was obtained by pressing, and then a molded article was obtained in the same manner as in Example 1. The results are shown in Table 1. The reinforced polypropylene sheet mentioned above expands only about 1.3 times,
It did not become porous. Comparative Example 4 Sheets with thicknesses of 1.5 mm and 0.4 mm were obtained in the same manner as in Example 2. This and Glasslon Container Strand Matsut (manufactured by Asahi Glass Fiber)
CSM8600, 450g/m ² ), surface resin layer 1.5mm/
2 pieces of Glasslon continuous strand mat / intermediate resin layer 0.4mm / 2 pieces of Glasslon continuous strand mat / surface resin layer
They were laminated to a thickness of 1.5 mm and pressed to obtain a reinforced polypropylene sheet. Next, a molded article was obtained in the same manner as in Example 1. The results are shown in Table 1. The reinforced polypropylene sheet expanded only about 1.4 times and did not become porous.

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Claims (1)

[Claims] 1 A sheet-shaped composite consisting of a modified polyolefin or a mixture of a modified polyolefin and an unmodified polyolefin in which the amount of reactive maleic anhydride is in the range of 0.003 to 0.1% by weight, and glass fibers whose length is mostly 1 cm or more. A glass fiber reinforced polyolefin sheet for press molding, characterized in that the sheet expands in the thickness direction of the sheet and becomes porous when heated above the melting point or softening point of the polyolefin.