JPS6047295B2 - Reinforced polyolefin molding material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyolefin molding materials reinforced with gypsum needle crystal fibers.

The purpose is to provide a polyolefin molding material that is excellent in moldability, appearance, shape, thermal stability, dimensional stability, especially mechanical properties, and heat resistance, and has low molding machine wear and anisotropy of physical properties. Polyolefins are used as general purpose plastics.
Widely used for injection molded products, films, sheets, etc.

However, polyolefins such as polyethylene and polypropylene have insufficient mechanical properties and thermal properties under high loads, and have a large shrinkage rate during molding. PP is widely used in applications where mechanical and thermal properties are required. Although FR-PP reinforced with glass fibers has excellent mechanical and thermal properties in samples with oriented glass fibers, it has poor mechanical properties in the direction perpendicular to the orientation of glass fibers (with significant anisotropy). ), product design is difficult due to large anisotropy in molding shrinkage due to orientation, and glass fibers wear out molding machines and molds. In order to overcome these drawbacks, so-called inorganically reinforced oPP filled with particulate fillers such as talc have recently been developed. This is a mechanical property,
Although it has the advantage of less anisotropy in molding shrinkage, it has the disadvantage that its mechanical properties and thermal properties are inferior to FR-PP. Furthermore, gypsum fibers and their manufacturing method are well known, as shown in, for example, U.S. Pat. No. 3,822,340. It was found that almost no reinforcing properties were observed even when composited with polyolefin. As a result of intensive research to solve the above-mentioned drawbacks, the present inventor has arrived at the present invention, which has a diameter of about 2
Approximately 10% by weight or more of at least one kind of acicular crystal fibers of α-hemihydrate gypsum, ■-type anhydrite, or ■-type anhydrous gypsum, which is less than μ and has a length-to-diameter ratio of about 5 or more in the molding material. Desirably 10 to 7% by volume, more preferably 20%
This relates to a polyolefin molding material that is characterized by containing ~5% by weight.The characteristics of this material are that it uses an inexpensive material called gypsum, has excellent mechanical properties and thermal properties, and is easy to use in molding machines and molding metals. There is no wear on the mold, and there is little anisotropy in mechanical properties and molding shrinkage rate.The invention will be described in detail below. The acicular gypsum crystal fibers used in the present invention have a diameter of about 2μ or less, and are α-1hemihydrate gypsum, ■-type anhydrous gypsum,
(2) Any type of anhydrous gypsum may be used, or a mixture may be used.

As shown in Example 1, its production involves dispersing calcined gypsum in water, and if necessary, adding dihydrate gypsum powder to adjust the aqueous slurry concentration to 35% by weight or less. While stirring, the slurry is heated under pressure to obtain a slurry containing hemihydrate gypsum needle crystals, which is then dried separately to obtain α-hemihydrate gypsum needle crystal fibers. Furthermore, if necessary, the fiber may be dried at 170'C or higher to form a ■-type anhydrous gypsum or sintered to obtain a ■-type anhydrous gypsum needle-like crystal fiber. A mixture of these may also be used, and if necessary, surface treatment may be applied to improve adhesion to polyolefin. The gypsum needle crystal fiber thus obtained is mixed with three polyolefins such as polypropylene and polyethylene,
Pellets are manufactured by adding modified polyolefin as necessary, and then injection molding, blow molding, extrusion molding, and
Performs calender molding, melt spinning processing, etc.

For the production of 4 pellets, a two-roll, Panbury mixer, single-screw extruder, twin-screw extruder, and special compound kneader are used. In either case, conditions must be set so that the length-to-diameter ratio (aspect ratio) of the gypsum needle crystal fibers is 5 or more, but any kneading machine can be used as long as the aspect ratio is 5 or more. . The polyolefin used in the present invention includes polypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, medium-low pressure polyethylene, etc., used alone or in combination.

Further, as the modified polyolefin, a polyolefin modified by grafting or adding one or more monomers of unsaturated fatty acids, unsaturated acid anhydrides, and epoxy-containing unsaturated compounds may be added or used alone. From the viewpoint of physical properties, it is preferable to add such a modified polyolefin. The acicular gypsum crystal fibers of the present invention must have a diameter of about 2μ or less and 7 or less, and the ratio of the fiber length to diameter (aspect ratio) in the molding material must be at least 5 or more.

Figure 11 shows 4% by weight of gypsum needle crystal fibers, 54% by weight of polypropylene (M1=5), and 54% by weight of modified polypropylene (M1=5).
(modified with 20.6% acrylic acid) in the case of 6% by weight,
This shows the relationship between aspect ratio and tensile strength. It can be seen that in the present invention, when the aspect ratio is about 5 or more, the tensile strength increases significantly. The ■-type anhydrite acicular crystal fiber manufactured based on U.S. Pat. No. 3,822,340 described as a comparative example has an aspect ratio of only 10 at maximum.
The tensile strength is lower than that of the present invention. Specifically, in the case of the present invention, the tensile strength when the aspect ratio is 4 to 8 is 351k9/C.
lt, whereas the comparative example has only 318k9/c. In addition, in the case of the comparative example, it is difficult to achieve an aspect ratio of 10 or more using normal processing methods, whereas in the case of the present invention,
Since the diameter of the fibers is as thin as 0.5 to 1.5μ, the aspect ratio can be increased. Figure 2 shows aspect ratio and heat distortion temperature (
18.6kg/d). When the aspect ratio becomes 5 or more, a significant improvement is observed. In the present invention, the filling amount is about 1% by volume or more, preferably 10-7% by volume, and more preferably 20-5% by volume.

The figure shows the tensile strength and heat distortion temperature when the diameter is about 2μ or less and the aspect ratio of the gypsum fibers in the molded product is about 5 or more.
Shown in 3 and 4. In both cases, a significant improvement is seen when the content is 10% by weight or more. Next, the effect of the present invention on anisotropy due to fiber orientation will be described. When filled with glass fibers, there are significant differences in physical properties and molding shrinkage rate depending on the orientation of the fibers. This orientation becomes more pronounced as the aspect ratio of the glass fiber increases. When glass fiber is filled into polyolefin or the like, the kneading machine, molding machine, or mold is subject to severe abrasion, so that only 30% by weight or less can be filled. Therefore, in order to obtain the maximum effect with a small amount of filling, it is necessary to increase the aspect ratio of the fibers, and as a result, the difference in physical properties due to orientation becomes large. In the case of the present invention, as shown in Example 2, high filling is possible because no equipment wear occurs at all, and because there is little fiber orientation, anisotropy in physical properties and molding shrinkage rate can be reduced. In the case of glass fiber (g) the tensile strength increases by 3% by weight.
The anisotropy of 30 to 592 kg/c results in a mold shrinkage rate of 0.
Anisotropy of 17% to 0.8% occurs, but in the present invention, the tensile strength is 425 to 466k9/Cdl, and the molding shrinkage rate is 0.5.
It exhibits only an extremely small anisotropy of ~0.65%, and high physical properties can be obtained. This is extremely advantageous in practice. That is, when designing a product, if there is anisotropy in the strength, it is necessary to design it with the weakest strength, and the greater the anisotropy, the higher the strength in the most oriented direction becomes. Also, if there is anisotropy in the molding shrinkage rate, dimensional accuracy cannot be achieved.
It is necessary to have as little anisotropy as possible and a low shrinkage rate. Since the present invention has less anisotropy in both strength and molding shrinkage, it can be said to be much more advantageous than glass fiber filling from a practical standpoint. In addition, in the case of the present invention, since the filler is a soft material called gypsum, there is no wear on the processing machine, so there is no need to take measures against wear when molding polyolefin by filling it with glass fibers. From this point of view, it can be said to be a useful material. Further, substances commonly used for coloring, increasing weight, modifying, etc. may be added to the molding material of the present invention within a range that does not cause any adverse effects.

As is clear from the above, the molding material of the present invention has excellent moldability, shape, thermal stability, dimensional stability, mechanical properties, and heat resistance, especially strength and heat resistance, and has excellent molding machine wear and strength and molding shrinkage. Shows excellent performance with less tropism.

The molding material of the present invention is used in molding processes such as extrusion molding, blow molding, injection molding, calendering, and melt spinning, and exhibits unique characteristics. Example 1 1 kg of calcined gypsum was added to 9k9 of 25 C water and stirred for about 3 minutes to create a fine dihydrate gypsum slurry. This slurry was put into a reaction tank and heated for 1 hour while stirring at 120 r'Pm.
After heating at 30'C for 5 minutes, water vapor was released, the liquid temperature in the reaction tank was cooled to 105°C, the slurry was discharged, immediately filtered, washed with methyl alcohol, and then dried at a temperature of 110°C. .

The obtained α-1hemihydrate gypsum needle-like crystal fibers have a diameter of 0.5~
1.5μ, length 80-150μ. When this α-hemihydrate gypsum needle-like crystal fiber is dried at 700° C. for 1 hour, a ■-shaped anhydrous needle-like crystal fiber having a diameter of 0.5 to 1.5 μm and a length of 80 to 150 μm is obtained. This gypsum acicular crystal fiber 4% by weight, polypropylene (M1=5) 54% by weight, modified polypropylene (6% acrylic acid graft, MI=20) 6
They were blended in a proportion of % by weight and extruded into pellets using a conventional method. This pellet was injection molded, and the relationship between aspect ratio and physical properties was determined. For comparison, U. S. ■-type anhydrite acicular crystal fibers were produced by the method described in issue P38223.

The diameter of the fibers is 2-6μ and the length is about 100μ. This was pelletized and injection molded using the above formulation to determine its physical properties and aspect ratio. The results are shown in Table 1 and Figures 1 and 2.
From FIG. 1, it can be seen that in the present invention, when the aspect ratio is about 5 or more, the tensile strength is significantly improved.

The same applies to bending strength. From FIG. 2, the same can be said about the heat distortion temperature. On the other hand, in the comparative example, even if the aspect ratio is increased to 5 or more, the strength is not improved as in the present invention.
Example 2 In the case of the present invention, the strength is 425 kg/C at the weakest point.
The anisotropy is small at 466 kg/Cfl at high ltl, and the anisotropy of the molding shrinkage rate is also slight, but it can be seen that the anisotropy of the strength and molding shrinkage rate is extremely large in comparison with the glass fiber filling of the example.

Example 4 w? No-l-mi-I1 1 eight no. '2n/* The ■-type anhydrous gypsum needle-like crystal fiber of Example 1 was blended with a mixture of polypropylene (M1=5), 9% by weight, and monomodified polypropylene (6% modified with acrylic acid, M1=20) by 1% by weight. death,
The content of the same fiber is 10, 20, 30, 40, 5%
The aspect ratio of the same fiber in the molded product is 5.
It was molded to look like this.

The results are shown in Table 2 and Figures 3 and 4. From the above results, it can be seen that when the gypsum needle-like crystal fibers are filled in an amount of 1% by weight or more, preferably 20% by weight or more, the tensile properties, bending properties, and heat distortion temperature significantly increase. In addition, continuous injection molding of 1011 Terama was carried out using pellets filled with 50% by weight, but no wear was observed on the molding machine.

Example 3 ** The pellets filled with 5 weight percent of Example 2 were molded into a flat plate using a mold with a film gate.

For comparison, 114 inches of glass fiber was filled at 3% by heel weight and molded in the same manner. The aspect ratio of the glass fiber molded product was 80 to 100. Test pieces were cut out from this flat plate in the flow direction and in the direction perpendicular thereto, and the tensile strength and molding shrinkage rate were measured. The results are shown in Table-3. Table -
As can be seen from 4, polyethylene has the same effect as polypropylene.

Example 5 In the same manner as in Example 1, 4% by weight of the gypsum acicular crystal fibers α-hemihydrate type and ■-type anhydrous fibers were filled into a mixture of polypropylene and modified polypropylene and processed in the same manner. did.

The physical properties when the aspect ratio is 10 to 25 are shown in Table-
5, and it was found that it had the same effect as the ■-type anhydrous gypsum needle crystal fiber.

[Brief explanation of the drawing]

Figure 1 illustrates the relationship between aspect ratio and tensile strength for the present invention and comparative examples for a molding material consisting of 40% by weight of ■-type anhydrite acicular crystal fibers, 54% by weight of polypropylene, and 6% by weight of modified polypropylene. .

Claims (1)

[Claims] 1 α-hemihydrate gypsum, I, having a diameter of about 2μ or less and a length-to-diameter ratio of gypsum needle crystal fibers in the molding material of about 5 or more;
A reinforced polyolefin molding material characterized by containing 10% by weight or more of type II anhydrous gypsum or at least one kind of acicular crystal fiber of type II anhydrous gypsum. 2. The reinforced polyolefin molding material according to claim 1, which contains 10 to 70% by weight of gypsum needle crystal fibers. 3. The reinforced polyolefin molding material according to claim 1, which contains 20 to 50% by weight of gypsum needle crystal fibers. 4. The reinforced polyolefin molding material according to claim 1, wherein the polyolefin is one or a mixture of two or more of polypropylene, ethylene-propylene copolymer, ethylene-propylene block copolymer, and medium-low pressure polyethylene.