JPS6017302B2 - Reinforced polyvinyl chloride resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the tensile strength and impact of the molded product by controlling the residual stress in the molded product made of gypsum needle crystal fibers and polyvinyl chloride resin to about 110×9/crucium or more. This invention relates to a composite polyvinyl chloride resin molded product with well-balanced strength improvements.

In recent years, research has been conducted in various fields aimed at improving mechanical strength, heat resistance, etc. by combining thermoplastic resins with fibrous reinforcing materials.

On the other hand, large amounts of calcium sulfite or gypsum are produced as by-products from flue gas desulfurization, and the effective use of this has been raised as an important issue, and various fields are considering its use as an inexpensive and fire-resistant filler. For example, a method has been proposed in which gypsum is made into needle-like crystals and used as a filler with reinforcing properties. Gypsum needle crystal fibers and methods for producing the same are known from various documents.

It is well known that the larger the diameter-to-length ratio of the fibers in a molded product made of a fibrous filler and a thermoplastic resin, the higher the tensile strength of the molded product. However, in general, in the case of short fiber-based fillers, the drop in the weight impact strength, which is important in the case of pipe molded articles, for example, is significantly reduced and poses a major practical problem. On the other hand, in a molded body made of gypsum needle crystal fibers and polyvinyl chloride resin, when the ratio of diameter to length of the gypsum needle crystal fibers in the molded body is about 10 or more, also exhibits high tensile strength.
However, even in this case, the drop in impact strength cannot be ignored and there is a problem in terms of balanced mechanical properties. The inventors of the present invention have conducted extensive research to solve the above-mentioned drawbacks, and as a result, the present inventors have developed a fabric made of gypsum needle-like crystal fibers and polychlorinated pinyl resin.

The residual stress in the compact can be reduced to approximately 11 by selecting processing conditions.
It has been found that if the impact strength of the molded product is increased to 0k9/k or more, the impact strength of the molded product is greatly improved, while the decrease in tensile strength is small, thereby making it possible to obtain a molded product with improved tensile strength and impact strength in a well-balanced manner. We have arrived at the present invention. in general,
When molding plastics, it is known that if the molding is performed in such a way that residual strain or residual stress remains unevenly in the molded product, the mechanical strength will drop particularly significantly, which is undesirable in terms of physical properties.

Here, residual strain or residual stress refers to the strain or force that remains in the molded product when the molding material is hardened during non-uniform or rapid cooling, stretching, compression, etc. during molding. . On the other hand, the artificially applied average and orderly residual stress improves the physical properties of the product, so
For example, in the case of pipe forming, measures are taken to actively increase this size. However, in a composite material made of a composite of substances with very different properties, extremely large residual stress is localized near the interface of dissimilar materials during molding (cooling process), mainly due to the difference in their thermal expansion coefficients. occurs as a result of This residual stress is amplified by the rapid cooling process, and is easily caused by peeling at the interface of different materials, immediately after molding, or under adverse environments, and further progresses to stress cracking of the entire product. This phenomenon is particularly noticeable in the case of fiber-based composite materials. Therefore, great care is taken during manufacturing to minimize the generation of residual stress in composite materials. Although tensile strength can be increased by efforts to prevent the generation of such residual stress, impact strength is not only not improved but also tends to decrease. On the other hand, in a molded product made of gypsum acicular crystal fibers and polyvinyl chloride resin, even when the gypsum acicular crystal fibers are contained in a large amount of 1% by weight or more in the composite material, the gypsum acicular crystal fibers are Due to the very small shape of the acicular crystal fibers (for example, 1 to 2 peaks in diameter), the localization of residual stress near the interface of different materials during molding is very small, so to some extent it is due to artifacts. It is possible to give an ordered residual stress on average.

In this case, by increasing the average residual stress of the entire molded product to 110k9/sulfur or higher, it is possible to improve both tensile strength and impact strength in a well-balanced manner compared to the original polyvinyl chloride resin. U-tsuta. It is surprising that the mechanical strength of a composite material made of inorganic fibers and a thermoplastic resin can be improved in a well-balanced manner by increasing the residual stress in the composite material as in the present invention.

According to the present invention, it is possible to easily provide a composite polyvinyl chloride resin molded article having excellent mechanical properties using an inexpensive material such as gypsum.

It is preferable that the gypsum fiber has a small diameter, and it is particularly preferable that the diameter is 2 or less and the aspect ratio in the molded product is 10 or more.

The ratio of gypsum fibers in the molded product can be arbitrarily changed depending on the purpose of use, but in consideration of other physical properties, it can usually be used in an amount of 5 to 70 parts by weight per 100 parts by weight of vinyl chloride resin. The acicular gypsum crystal fibers used in the present invention may be any of B-hemihydrate gypsum, M-type anhydrous gypsum, O-type anhydrous gypsum, or a mixture thereof.

As shown in Example 1, its production is as follows: calcined gypsum is dispersed in water, and if necessary, dihydrate gypsum powder is further added to adjust the aqueous slurry concentration to 35% by weight or less, and hemihydrate gypsum needle crystal fibers are produced. While heating under pressure until obtained, it is heated under pressure to form a slurry containing hemihydrate gypsum needle crystals, and dried in an oven to obtain Q1 hemihydrate gypsum needle crystal fibers. Furthermore, if necessary, it may be dried at 170° C. or higher to produce M-type anhydrous or calcined needle-shaped O-type anhydrous gypsum crystals. Also, a mixture of these may be used, and if necessary, surface treatment may be applied to improve adhesion to polyvinyl chloride resin. The gypsum needle crystal fibers obtained in this way are mixed with polychloride pinyl resin and compounding agents such as stabilizers, lubricants, processability improvers, etc. Either directly obtain the molding material using a special compound moat kneader, or manufacture pellets using a two-roll, Banbury mixer, single-screw extruder, twin-screw extruder, or special compound kneader.
Alternatively, a molding material may be obtained by injection molding, blow molding, extrusion molding, calendar molding, melt spinning processing, etc. using a powder compound. Although there are no limitations to the kneading and molding machine in either case, it is particularly preferable to apply the method of the present invention to the manufacture of pipes, irregularly shaped products, etc. by extrusion molding. The polyvinyl chloride resin in the present invention refers to polyvinyl chloride resin, polyvinylidene chloride resin, vinyl chloride/pinylidene chloride copolymer, pinyl chloride/vinyl acetate copolymer, vinyl chloride/maleic anhydride copolymer. ,
It includes copolymers such as pinyl chloride/ethylene copolymer, vinyl chloride/propylene copolymer, and modified resins such as chlorinated polypinyl chloride resin, and these may be used alone or in combination. It is also possible.

Further, resins for improving impact resistance such as ABS and MBS can also be mixed. The present invention is a molding material made of gypsum needle-like crystal fibers and a polyvinyl chloride resin, and is characterized in that the residual stress in the molded product is 110 k9/base or more.

The residual stress referred to in the present invention refers to a sample piece that is treated in a hot air dryer kept at 125°C for one hour, and then the residual strain is determined from the shrinkage rate of the test piece. The residual stress is defined as the product multiplied by

The sample piece is about 6cm long, about 1.5cm wide, and about 3cm thick from the molded product.
Create by cutting out willow. The elastic modulus is measured according to JIS K6745 method. Residual stress 110k9
For example, in order to control the sizing part during extrusion processing, the temperature of the mold during injection molding processing or the cooling section during press molding processing is lowered and the cooling rate is increased. Ru.

The residual stress can also be increased by stretching during extrusion. When the residual stress is increased in this manner, the tensile strength of the molded product slightly decreases, but the impact strength is significantly improved, and the mechanical strength is improved in a well-balanced manner. However, it should be noted that even if the residual stress is increased excessively, the effect tends to decrease on the contrary. Usually 300k9/carp or less, preferably 110-250k9
/It's good to be your enemy. The method of the present invention will be described in more detail by way of examples.

The tensile properties were measured by the JIS K6745 method, and the impact strength was measured by DuPont falling weight impact strength. DuPont impact strength: 2.5-2.7 Willow, lead, weight: 300
This is the half-destruction height. Next, examples will be shown. Example 1 1 kg of calcined gypsum was added to 25 qo of 9k9 water and stirred for about 3 minutes to create a fine dihydrate gypsum slurry. This slurry was put into a reaction tank and heated at 12 pm for 1 hour.
After heating at 30 qC for 5 minutes, steam was released, the liquid temperature in the reaction tank was cooled to 105 pm, the slurry was discharged, immediately filtered, washed with methyl alcohol, and then heated to 110 qC.
It was dried at a temperature of q○.

The obtained Q-hemihydrate gypsum needle crystal fibers have a diameter of 0.5~
1.5 mm, length 80-150 r. When this Q-1 hemihydrate gypsum needle-like crystal fiber is dried for 700 hours, an O-type anhydrous needle-like crystal fiber having a diameter of 0.5 to 1.5 A and a length of 80 to 150 mm is obtained. 1% by weight of this gypsum needle-like crystal fiber, 81% by weight of polychlorinated pinyl resin (degree of polymerization 1000), and lead-based compounding agents were mixed and processed under various conditions to determine the relationship between residual stress in the molded product and physical properties. I asked for The results are shown in Table 1. However, processing method C. D. E is extrusion molding,
The temperature of the sizing part was set to high temperature (using 50 to 60 qo warm water), room temperature, and low temperature (using ice water), respectively, and cooling. Processing method A is molded by processing method D at a temperature slightly higher than the glass transition temperature of polyvinyl chloride resin (105o).
After pressing for 2 hours, the mixture was gradually cooled to room temperature. In processing method B, the molded product according to processing method D was heat treated in a hot air dryer for 2 hours at a temperature slightly lower than the glass transition temperature of the polyvinyl chloride resin, and then gradually cooled to room temperature. Table 1.1 From Table 11, it can be seen that when the residual stress in the molded product is about 110k9' average or more, the tensile strength and impact strength are improved in a balanced manner.

Example 2 Even when tin-blended polyvinyl chloride resin (polymerization degree 700) was used instead of lead-blended polyvinyl chloride resin in Example 1, the tensile strength and impact strength were balanced when the residual stress was about 110 k9/min or higher. You can see that it has been improved.

The results are shown in Table-2. * Processing method A. B. C. D. E
was carried out according to Example 1. Table 2 2

Claims (1)

[Claims] 1. A reinforced polyvinyl chloride resin molded article comprising gypsum acicular crystal fibers and a polyvinyl chloride resin, and characterized in that the residual stress in the molded article is about 110 kg/cm^2 or more.