JPH0133486B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing high-strength molding materials, and in particular to a method for producing high-strength molding materials based on unsaturated polyester resins. Unsaturated polyester resin with a softening temperature of 60℃ or higher,
Powder-like, flake-like, or granular molding materials (hereinafter referred to as dry primics), which are composed of at least essential components cross-linking agents, fillers, and reinforcing fibers that are solid at room temperature, are easy to handle and suitable for mass production of molded products. It is put into practical use as suitable. That is, it is easy to measure, has good storage stability and flow characteristics during molding, and is suitable for compression molding, transfer molding, or injection molding, so it is effectively used in various fields. When this type of dry premix is applied to, for example, injection molding, it is preferable to use it in the form of flakes or pellets with small particle size from the viewpoint of improving measurement and workability. In this case, in order to improve the mechanical strength of the resulting molded product, long reinforcing fibers are included as one component in the dry premix. However, there is a limit to the amount of reinforcing fibers that can be blended, and the reinforcing fibers are easily broken into short pieces during the process of kneading and turning into flakes or pellets, so that the reinforcing effect on the resulting molded product cannot be fully demonstrated. There's a problem. For this reason, attempts have been made to appropriately select the molecular weight per double bond in the unsaturated polyester resin as a measure to improve the strength of the molded products obtained. I can't get anything. It has also been attempted to add a portion of a liquid crosslinking agent such as diallyl phthalate or triallyl cyanurate to a solid crosslinking agent to appropriately adjust the crosslinking density. However, in this method, since the viscosity of these liquid crosslinking agents is high,
The obtained composition has a high melt viscosity and the load on the reinforcing fibers increases during kneading of the composition, causing damage or deterioration of the reinforcing fibers, making it difficult to obtain a sufficient reinforcing effect. I can't. For this reason, attempts have been made to add and blend an appropriate amount of an organic solvent such as acetone, methanol, or toluene to the composition to lower the melt viscosity of the composition before heating and kneading it. however,
With this method, it is difficult to completely remove the above organic solvent from the dry primics obtained.
During molding, foaming of the residual organic solvent may generate pinholes or cavities in the molded product, resulting in structural defects in the molded product. As a result of extensive research in order to eliminate the drawbacks of these conventional methods, the present inventors have developed a liquid cross-linking agent with a viscosity of centipoise or less at 25°C as a component of the cross-linking agent based on the total weight of the molding material.
The present invention was completed based on the knowledge that when 0.2 to 1.0% by weight is added, the melt viscosity of the resulting composition is suitably reduced, the heating and kneading work proceeds smoothly, and molded products with excellent mechanical strength can be obtained. I came to the point. That is, the present invention provides a method for producing a flaky or granular unsaturated polyester molding material in which at least an unsaturated polyester resin, a crosslinking agent, a filler, reinforcing fibers, and a curing catalyst are mixed and kneaded under heat. The technical feature is that a liquid crosslinking agent having a viscosity of 1 centipoise or less at 25°C is blended as one component in an amount of 0.2 to 1.0% by weight based on the total weight of the molding material. The solid unsaturated polyester resin used in the present invention may be any unsaturated polyester resin that is solid at room temperature, and its composition or manufacturing method is not particularly limited. For example, as an acid component, 70 to 30 mol% of α, β unsaturated dicarboxylic acids such as maleic anhydride, fumaric acid, itaconic acid or a mixture of one or more of their anhydrides, phthalic anhydride, isophthalic acid, terephthalic acid , tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, adipic acid, chlorendic acid, and other saturated dicarboxylic acids or one or two of their anhydrides.
30 to 70 mol% of a mixture of more than one species and a polyhydric alcohol component such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4-
One or more selected from cyclohexanediol, 1,3-butanediol, diethylene glycol, dipropylene glycol, isopentyl glycol, neopentyl glycol, hydrogenated bisphenol A, etc. are used as a reaction component and N ₂
An unsaturated polyester resin having an acid value of 30 or less and a softening temperature of 70 to 110°C obtained by esterification reaction at 120 to 210°C in a gas atmosphere is preferred. In addition, examples of the crosslinking agent used in the present invention include those that are solid at room temperature, such as diallylphthalate prepolymer, N-vinylcarbazole, acrylamide, maleimide, and methacrylamide. A portion thereof may be replaced with a crosslinking agent having a high viscosity at room temperature such as diallyl phthalate monomer, diallyl isophthalate monomer, triallyl isocyanurate, N-vinylpyrrolidone, or dimethyl ichconate. Furthermore, examples of curing catalysts used in the present invention include tert-butyl perpenzoate, 2,5-dimethyl-2,5
-di(t-butylperoxy)hexane, 2,5
-dimethylhexane-2.5-di(peroxybenzoate), dicumyl peroxide, di-t-
Examples include butyl peroxide. The present invention is characterized in that, in addition to the above-mentioned crosslinking agents, a liquid crosslinking agent having a viscosity of 1 centipoise or less at 25° C. is blended. As this liquid cross-linking agent, any cross-linking agent (monomer) that reacts with the double bonds in the unsaturated polyester resin can be used. ,
Vinyl toluene monomer, acrylic acid methyl ester monomer, methacrylic acid methyl ester monomer, etc. are preferable. The amount of these crosslinking agents added to the dry Primics is 0.2% based on the total weight of the Dry Primics.
It is set within the range of ~1.0% by weight. The blending amount is 0.2
If it is less than % by weight, the melt viscosity during heating and kneading will not be sufficiently reduced, leading to damage and deterioration of the reinforcing fibers.
The mechanical strength of the molded product does not improve. If the content exceeds 1.0% by weight, the damage and deterioration phenomena of the reinforcing fibers will be reduced and the mechanical strength of the molded product will improve, but the resulting dry primics will be too soft and will not be processed during the pulverization or pelletizing process after heating and kneading. This not only causes clogging of the crusher or pelletizer, significantly impairing workability, but also causes a blocking phenomenon when the flakes or granules are left at room temperature, significantly reducing their storage stability. Furthermore, these liquid crosslinkers have a viscosity of 25
A material with a temperature of 1 centipoise or less at °C is used. If the viscosity becomes higher than this, during heating and kneading,
Because the melt viscosity of dry Primics does not decrease appropriately, the reinforcing fibers are more prone to damage and deterioration. As the filler used in the present invention, any filler used in ordinary dry molding materials can be used, such as calcium carbonate, aluminum hydroxide, talc, silica powder, clay, and the like. Further, as reinforcing fibers, in addition to inorganic fibers such as glass fibers and asbestos fibers, organic fibers such as vinylon fibers, acrylic fibers, and hemp may be blended as necessary. In addition, a release agent, a pigment, an anti-deterioration agent, etc. can be added to the dry pre-mix, if necessary. The present invention will be explained below based on examples. Example (1) Production of solid unsaturated polyester resin 4 mol of isophthalic acid, propylene glycol
After esterifying 10.3 mol at 120 to 190℃ under _N2 gas atmosphere to an acid value of 20, the temperature was increased to 140℃.
6 mol of maleic anhydride was added to this, and the acid value was further increased at 140 to 220°C under an _N2 gas atmosphere.
25 to obtain a solid unsaturated polyester resin with a softening temperature of 87°C. (2) Production of dry Primics The unsaturated polyester resin produced in (1) was ground into fine powder, and mixed in powder form with a crosslinking agent, filler, coloring agent, reinforcing fibers, etc. using a mixer. Next, the obtained mixture was heated and kneaded using an extruder equipped with a pelletizer equipped with a plurality of extrusion ports to produce granular dry premixes (molding material) having a particle size of 4 mm or less. (3) Injection molding Using the dry Primics prepared above as the molding material, using a screw-type injection molding machine, the cylinder temperature is 60 to 90℃, the nozzle temperature is 90℃, and the mold temperature is 160℃.
Strength test specimens were molded under molding conditions of ~170°C and a molding cycle of 90 seconds. (4) Measurement of Mechanical Properties The bending strength, tensile strength, and Shapey impact strength of the molded product made of the dry Primics obtained above were measured based on JISK6911. The above results are collectively shown in Table 1 for various dry primics. In addition, as a comparative example, the results obtained when the liquid crosslinking agent used in the present invention was not mixed are also listed. Furthermore, the blocking phenomenon in the table is the result when dry Primics was stored in air at 40°C for 96 hours. The viscosity of the liquid crosslinking agent used was 25
It was 0.8 centipoise in °C.

【table】

[Table] As is clear from Table 1, the molding materials of the comparative examples have lower mechanical strength than the materials according to the present invention, or even when the mechanical strength is high, a blocking phenomenon occurs, making them unsuitable as dry molding materials. Not only that, but when cutting into pellets with a pelletizer, the pellets were too soft and difficult to cut, and uncut glass fibers protruded from the pellets in the form of whiskers, significantly impairing hopperability.

Claims (1)

[Claims] 1. A method for producing a flaky or granular unsaturated polyester resin molding material, which comprises mixing at least an unsaturated polyester resin, a crosslinking agent, a filler, reinforcing fibers, and a curing catalyst, and kneading the mixture under heating. As a component of the agent, the viscosity at 25℃ is 1.
A method for producing a high-strength molding material, which comprises blending a liquid crosslinking agent of centipoise or less in an amount of 0.2 to 1.0% by weight based on the total weight of the molding material.