JPS6137297B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a glass fiber reinforced polypropylene molding material having excellent physical properties. Generally, polypropylene has excellent physical and chemical properties and is widely used as a general-purpose molding material. However, when reinforcing it with a reinforcing material such as glass fiber with the main purpose of improving its heat resistance and rigidity, the reinforcing effect is small compared to other thermoplastic resins such as nylon, polycarbonate, styrene resin, etc., and it is difficult to mix easily. A practically satisfactory composite material cannot be obtained by using only this method. This is basically due to the fact that polypropylene does not have reactive functional groups and has poor adhesion to glass fibers, but to compensate for this drawback, silane-based coupling agents etc. are used to bond the fibers to glass fibers. Surface treatment is commonly used, and although some effects have been obtained, satisfactory results have not been obtained. There is also a method in which the surface of glass fibers is treated with a silane coupling agent, and a suitable compound that has a functional group reactive with the coupling agent and has excellent compatibility with polypropylene is added as a third component. Although there are some examples where this has actually been done, in these cases too, fully satisfactory results have not been obtained. In addition, as another method, it has been reported to use modified polypropylene obtained by copolymerizing or graft polymerizing unsaturated carboxylic acids such as acrylic acid and maleic anhydride with polypropylene, and this method has been reported to be quite effective. There are, but it is still far from sufficient. However, according to this method, a strong chemical bond is formed between the carboxyl group and the silane coupling agent, which is a treatment agent for glass fibers, resulting in excellent adhesion between polypropylene and glass fibers. Systems using polypropylene show much better heat resistance and mechanical strength than systems using only a silane coupling agent or systems with the addition of a third component, but along with these effects, the use of modified polypropylene This caused various problems. In particular, modified polypropylene is much more hygroscopic than the base resin polypropylene, so it can cause problems such as foaming during extrusion processing, worsening operational stability, and also has physical properties that are affected by foaming. Since it contains air bubbles, voids are generated at the interface between the glass fiber and the matrix resin, and the effect of improving adhesion using modified polypropylene is often not sufficiently achieved. The present invention relates to a glass fiber-reinforced polypropylene molding material that uses modified polypropylene when reinforcing polypropylene with glass fibers, solves the above-mentioned problems, and has dramatically improved physical properties compared to conventional ones. The present invention is a mixture consisting of 95 to 70 wt% of polypropylene (A) and 5 to 30 wt% of glass fiber (B) treated with an aminosilane coupling agent of 0.02 to 0.2 PHR and an epoxy resin of 0.2 to 1.2 PHR based on the glass fiber. To A+B), modified polypropylene (C) containing acrylic acid or maleic anhydride was added such that the weight ratio of acrylic acid or maleic anhydride to glass fiber (B) was in the range of 0.01 to 0.06. This article relates to a strong glass fiber-reinforced polypropylene molding material obtained by pressing the mixture (A+B+C) in a vented extruder at a reduced pressure of 500 mmHg or more, and specific study results are shown in Examples. The polypropylene used in the present invention is a crystalline polypropylene commonly referred to as polypropylene, and the content in the propylene homopolymer and propylene copolymer is 15 wt%.
By this we mean essentially crystalline copolymers with other α-olefins, such as ethylene. In addition, as a treatment agent for glass fibers, it is best to add aminosilane at 0.02 to 0.2 PHR as a coupling agent and epoxy resin at 0.2 to 1.2 PHR as a sizing agent.Other coupling agents include vinyl silane, acrylic silane, epoxy silane, etc. Further, as a sizing agent, vinyl oxide and the like were investigated, but results comparable to those obtained when using the above-mentioned processing agent were not obtained. In addition, in the case of coupling agents, the amount added is based on glass fiber.
0.02PHR or more, preferably 0.04PHR or more,
The practical upper limit is 0.2 PHR, and adding more than that will not improve physical properties such as mechanical properties and heat resistance. In addition, in the case of a sizing agent, it should be 0.2PHR or more, preferably 0.3PHR or more, and the upper limit is 1.2PHR.
Up to this point is practical, and even if more than that is added, no improvement in physical properties is observed, and on the contrary, problems such as coloring occur in terms of thermal stability. In addition, the reinforcing effect of glass fiber becomes noticeable as the concentration of glass fiber in the mixture increases.
A range of 5 wt% or more to 30 wt% is practical; if it exceeds this, the balance in terms of physical properties will be poor and manufacturing will also become difficult. The modified polypropylene used in the present invention is produced by adding maleic anhydride or acrylic acid together with an organic peroxide to a predetermined amount of polypropylene, and melt-kneading the mixture in a commonly used extruder.
The concentration of maleic anhydride or acrylic acid in the modified polypropylene may be arbitrary, but from the viewpoint of the thermal stability of the modified polypropylene, the grafting rate, etc., it is appropriate to range from 2.0 to 6.0 wt%. The concentration of is determined by the concentration of glass fibers (amount of treatment agent) in the mixture, and if the concentration of treatment agent for glass fibers is as described above, the ratio of glass fibers to acrylic acid or maleic anhydride is 0.01 to 0.01.
A value of 0.16 is appropriate; if it is less than 0.01, the modification effect is insufficient, and if it is more than 0.06, practical problems will occur, especially in terms of thermal stability. In addition, in the present invention, when mixing polypropylene, glass fiber, and modified polypropylene, the vented extruder is used to extrude from the vent part under reduced pressure with equipment such as a vacuum pump, and the VM of the product is
It is characterized by having (volatile content) less than 0.1wt%. Modified polypropylene is hygroscopic, so if it is extruded under normal conditions (open to the atmosphere) without reduced pressure, the molded product will foam, worsening operational stability, and in terms of physical properties, adhesion between the matrix polymer and glass fibers will occur. Because the condition deteriorates, the expected effect cannot be obtained. For this reason, in the past, pre-drying of modified polypropylene was carried out, but
Pre-drying only has the effect of slightly removing moisture adhering to the surface, which is extremely insufficient. In addition, as shown in the examples, VM (volatile content) must be kept at 0.1wt% or less, and if processed under reduced pressure, products with certain physical properties can be obtained, but 0.1wt% VM (volatile matter), satisfactory physical properties cannot be obtained. Note that VM (volatile content) means the volatile content expressed in weight % after heating and drying about 10g of a sample in a constant temperature dryer at 105°C for 5 hours. Furthermore, generally various antioxidants, stabilizers such as ultraviolet absorbers, general pigments, inorganic fillers, etc. may be optionally added to the molding material of the present invention.

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Claims (1)

[Claims] 1. A mixture consisting of 95 to 70 wt% of polypropylene (A) and 5 to 30 wt% of glass fiber (B) treated with 0.02 to 0.2 PHR of an aminosilane coupling agent and 0.2 to 1.2 PHR of epoxy resin based on the glass fiber (A+B) In contrast, the weight ratio of acrylic acid or maleic anhydride to glass fiber (B) is
VM (volatile content) obtained by extruding a mixture (A+B+C) in which modified polypropylene (C) containing acrylic acid or maleic anhydride is added to the range of 0.01 to 0.06 under reduced pressure using a vented extruder.
Tough polypropylene molding material less than 0.1wt%.