JPH0313048B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a flat injection molded product containing as essential components a crystalline aliphatic polyolefin resin having a melt viscosity within a specific range, mica powder, and an additive for improving the interfacial adhesive strength between the resin and the mica powder. Regarding. When manufacturing a molded article by injection molding using a thermoplastic resin, especially a crystalline aliphatic polyolefin resin such as polypropylene or polyethylene, the molded article may warp, especially if it has a flat plate shape. , twisting, and other phenomena occur. Warping or twisting of molded products not only significantly impairs the appearance of the molded product and lowers its commercial value, but also makes it difficult to assemble products using adhesives or mechanical means. This creates the problem of making it extremely difficult. It is empirically known that warping and twisting of molded products can be reduced through product design, for example by adding ribs, but this is not a desirable improvement method due to problems such as the complexity of the shape of the molded product. The development of a resin composition for injection molding that does not cause twisting is awaited. For example, it is possible to obtain molded products with extremely excellent elastic modulus, dimensional stability, heat resistance, and strength by blending mica powder with an aspect ratio of 30 or more, preferably 40 to 60% by volume, into various resins. Kimiaki
49-18615. However, resin compositions containing 40 to 60% by volume of mica powder with an aspect ratio of 30 or more do not warp or twist when subjected to injection molding, but have extremely poor flowability and the impact strength of molded products. , elongation, appearance, etc. are extremely unsatisfactory. For example, the Izotsu impact strength, which is most important as a practical performance of molded products, is much lower than the generally required minimum value of 10 kg cm/cm ² (without notches), as shown in the comparative example below. value. The value of 10 kg·cm/cm ² corresponds to the izod impact strength of a resin having the lowest izod impact strength among the resins currently widely used on the market, such as polystyrene and styrene-acrylonitrile resins. However, the present inventors discovered that there is no warping or twisting,
As a result of extensive research into developing a resin composition that satisfies practical physical properties such as impact strength and moldability, we have developed a mica-filled polyolefin resin composition using a resin with a melt viscosity within a specific range as the polyolefin resin. The present inventors have now completed the present invention by discovering that a composition that satisfies both of the above requirements can be obtained by adding an additive for improving the interfacial adhesive strength between the polyolefin resin and the mica powder. The resin used in the present invention is a crystalline resin family polyolefin resin, such as polypropylene resin (hereinafter abbreviated as PP), polyethylene resin (hereinafter referred to as PE resin), and copolymers containing these as main components. The melt viscosity of the resin used in the present invention needs to be within the range of 4 to 20 g/10 min, more preferably 8 to 20 g/10 min when expressed by melt index.
20g/10 minutes. The melt index referred to in the present invention is measured under a load of 2.16 kg at 230℃ in the case of PP or a resin whose main component is PP, and at 190℃ in the case of PE or a resin whose main component is PE. It is a value. Since the composition of the present invention contains additives to improve the interfacial adhesive strength between the resin and the mica powder, molecular chain scission and crosslinking reactions may occur due to heating during the production of the composition. In this case, the melt index of the resin changes, but the melt index in the present invention refers to the melt index of the resin contained in the composition of the present invention. If the melt index is smaller than the above range, warping and twisting of the molded product cannot be suppressed unless the mixing ratio of mica powder is extremely high.
The molded product has problems such as impact strength, weld strength, and surface roughness of the injection molded product. On the other hand, if the melt index is larger than the above range, there is no problem with the morphological stability of the molded article, but the physical properties of the molded article, particularly impact strength, elongation, strength, etc., are undesirably reduced. The mica powder used in the present invention includes:
A wide range of materials can be selected from muscovite, phlogopite, synthetic phlogopite, etc., but it is important that crystal water does not separate in the temperature range from the kneading temperature with the resin to the injection molding temperature. desirable. The ratio of the weight average diameter to the weight average thickness of the mica powder contained in the composition of the present invention, that is, the aspect ratio A and the content B of the mica powder in the composition, B weight %, must be within the range of the following formula. is necessary. -1.0A+35≦B≦-0.25A+50 (5≦A≦20) -0.2A+19≦B≦-0.25A+50 (20<A) B<-1.0A+35 (5≦A≦20) and B<-
For compositions in the range of 0.2A+19 (20<A), it is difficult to suppress warping and twisting of molded products, while for compositions in the range of B>-0.25A+50 (5≦A≦30), molded products Although warping can be suppressed, this is not desirable because the physical properties such as impact strength and elongation of the molded product decrease. The aspect ratio of mica powder in the present invention is, for example, as described in Ind.Eng.Chem.Fundam.Vol 12.No.1 (1973)
This is a numerical value measured by the method described in the document P124. Specifically, the weight average diameter of mica powder measured using a sieve and the surface of a predetermined weight of mica powder are subjected to lipophilic treatment, and the particles are suspended so as to form a single layer in a close-packed state on the water surface. This value is calculated from the weight average thickness of the mica powder, which is calculated by multiplying the occupied area by 0.75. There is no particular restriction on the diameter of the mica powder, but from the viewpoint of appearance and weld strength, the diameter of the mica powder in the molded product is preferably 200 μm or less. In the composition of the invention it is necessary to use additives to improve the interfacial adhesive strength between mica powder and resin. The types of additives vary depending on the type of resin, but generally include compounds that have a group that has affinity with the resin and a silanol group, which are collectively called silane coupling agents, unsaturated carboxylic acids or their anhydrides or esters, Unsaturated epoxy monomers, isocyanate compounds, etc. are used. For example, for aliphatic polyolefin resins,
vinyl-tris(β-methoxyethoxy)silane,
In addition to silane coupling agents such as γ-methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, maleic anhydride, acrylic acid, glycidyl methacrylate, tolylene diisocyanate, diphenylmethane 4,
4' diisocyanate, α-naphthyl isocyanate and the like are preferably used. In addition, when using these additives, it is necessary to use an organic peroxide together as necessary. Improvement of interfacial adhesion strength between resin/mica by additives means that the strength of injection molded products made from compositions using additives increases compared to the strength of injection molded products made from compositions without additives. Confirmed by. The use of these additives is effective in suppressing warping of injection molded products and also in improving the physical properties of molded products.
The mixing ratio of additives varies depending on the type of additive used and is not particularly limited, but is generally 0.05 to 3.0% by weight of the mica powder. There are no particular restrictions on the method of mixing the resin, mica powder, and additives; for example, the method of melt-mixing the resin with surface-treated mica powder prepared by spraying the additive onto the mica powder in a Henschel mixer, or the method of melt-mixing the resin with the additive. A method of melt-mixing mica powder with a modified resin obtained by melt-kneading with a resin, a method of melt-mixing a resin, mica powder, and additives at the same time, etc. can be adopted. The composition obtained by the method of the present invention can be injection molded into any shape by feeding it into a general injection molding machine. The characteristic of the composition, that is, the non-warping property is exhibited significantly. Various known additives such as antistatic agents, lubricants, colorants, and stabilizers can be used in the composition of the present invention, if necessary. Hereinafter, the method of the present invention will be explained in more detail with reference to Examples and Comparative Examples.
This is not intended to limit the invention in any way. Example 1 and Comparative Example 1 PP resin with a melt index of 8 g/10 minutes,
Three types of phlogopite powders A, B, and C with different diameters and aspect ratios at 10, 20, 30, 40, and 50% by weight, respectively.
After mixing in a tumbler mixer, the mixture was fed to an extruder to form pellets. Each pellet has a weight of mica powder mixed in the pellet.
Add 0.5% by weight of γ-aminopropyltriethoxysilane and stir thoroughly with a Henschel mixer, then feed to the extruder again and mix.
Extrusion was performed to obtain pellets. The weight average aspect ratio of the mica powder contained in the pellets is 28 in the case of phlogopite A, 17 in the case of phlogopite B, and 11 in the case of phlogopite C, and the weight average diameter of the mica powder is In the case of phlogopite A, 105 μ;
62μ for phlogopite B, and 62μ for phlogopite C.
It was 10μ. The obtained pellets were manufactured by Nikko Ankelberg V-15.
−75 type injection molding machine, cylinder temperature 250℃,
Injection molding was performed under the conditions of a mold temperature of 60℃, an injection pressure of 40Kg/cm ² (gauge pressure), and a molding cycle of 40 seconds.
1/2×1/2×2・1/2 for Izotsu impact strength measurement
Inch molded product, diameter 15cm for warp measurement, thickness
A 0.2 cm disc was molded. In the case of a disk, the gate is located at the center of the disk and has a diameter of 1.0 cmφ. The obtained disk was left in a constant temperature and humidity room at 23℃ and 65% RH for 48 hours, and then the warpage was measured using the method shown in Figure 1. Expressed by d×100. Figure 2 shows the measurement results of the Izot impact strength and warpage without a notch. As is clear from Figure 2, the warpage is less than 1%, and the Izotsu impact strength is 10Kg・cm/
Any resin composition that satisfies both requirements of cm ² or more falls within the range of the inequality expressed by formulas (1) and (2) defined in the claims. Example 2 and Comparative Example 2 Exactly the same experiment as in Example 1 and Comparative Example 1 was conducted using a PP resin with a melt index of 15 g/10 minutes. The weight average aspect ratio of the phlogopite powder contained in the pellets was 29 for phlogopite A, 18 for phlogopite B, and 13 for phlogopite C. As is clear from the experimental results in Figure 3, all resin compositions with an isot impact strength of 10 Kg cm/cm ² or more and a warpage of 1% or less are within the range of the inequality defined in the claims. . Comparative Example 3 Using a PP resin with a melt index of 3 g/10 min, the same experiment as in Example 1 and Comparative Example 1 was conducted, and the results are shown in FIG. As is clear from Figure 4, the warpage is less than 1% and the Izotsu impact strength is 10.
There is no area that satisfies both Kg・cm/cm ² . Comparative Example 4 Using a PP resin with a melt index of 25 g/10 minutes, the same experiment as in Example 1 and Comparative Example 1 was conducted, and the results are shown in FIG. As is clear from this figure, there is no region that satisfies both the Izot impact strength of 10 Kg·cm/cm ² or more and the warpage of 1% or less, which are the objectives of the present application. Comparative Example 5 An experiment was conducted under exactly the same conditions as in Example 1 and Comparative Example 1, except that γ-aminopropyltriethoxysilane was not used, and the results are shown in FIG. As is clear from this figure, even when the additives referred to in the present invention are not used, no material having the Izot impact strength as the object of the present invention and with suppressed warpage has been obtained. Example 3 0.1% by weight of γ-methacryloxypropyltrimethoxysilane and 0.01% by weight of dicumyl peroxide based on the resin weight were mixed with PP resin having a melt index of 4 g/10 minutes, and melt extrusion was performed at 230°C. Ta. The melt index of the obtained PP resin changed to 6.8 g/10 minutes. Phlogopite powder was blended into the modified PP resin and melt extrusion was performed again to obtain pellets with a phlogopite powder content of 20% by weight. The weight average aspect ratio of phlogopite powder in pellets is
It was 19. The pellets were injection molded under exactly the same conditions as in Example 1, and the warpage of the molded product was 0.5.
%, impact strength without notch is 20Kg・cm/cm ²
It was hot. Example 4 A PP resin having a melt index of 4 g/10 minutes was mixed with 0.5% by weight of maleic anhydride and 0.01% by weight of dicumyl peroxide based on the weight of the resin, and melt extrusion was performed at 230°C. The melt index of the obtained PP resin changed to 7.1 g/10 minutes.
Phlogopite powder was blended into the modified PP resin and melt extrusion was performed again to obtain pellets with a phlogopite mixing ratio of 30% by weight. The weight average aspect ratio of the phlogopite powder in the pellets was 12. The pellets were prepared in Example 1.
When injection molded under the same conditions as above, the warpage of the molded product was 0.4%, and the impact strength without notches was 0.4%.
It was 17Kg・cm/ ^cm2 . Example 5 The same experiment as in Example 4 was conducted except that acrylic acid was used instead of maleic anhydride.
The melt index of modified PP resin is 7.2g/10
The weight average aspect ratio of the mica powder in the composition was 12. The resulting molded product had a warpage of 0.3% and a notch-free isot impact strength of 16 kg·cm/cm ² . Example 6 and Comparative Example 6 Three high-density polyethylene resins with a melt index of 15 g/10 minutes and different diameters and aspect ratios were used.
Pellets containing 10, 20, 30, 40, and 50% by weight of seed phlogopite powder were prepared. 2% by weight of the phlogopite powder mixed into each pellet
A 50% by weight solution of 2.5-functional crude diphenylmethane diisocyanate in dioctyl phthalate (Millionate MR, manufactured by Nippon Polyurethane Co., Ltd.) was sufficiently stirred in a Henschel mixer and then fed to an extruder for mixing and extrusion to form pellets. I got it. The obtained pellets were manufactured by Nikko Ankelberg V-
Supply to 15-75 type injection molding machine, cylinder temperature
Injection molding was carried out under the following conditions: 220°C, mold temperature 60°C, injection pressure 40Kg/cm ² (gauge pressure), and molding cycle 40 seconds. The resulting molded product was measured for warpage and non-notched Izo impact strength in exactly the same manner as in Example 1, and the results shown in FIG. 7 were obtained. As is clear from this figure, any material that satisfies the requirements of warpage of 1% or less and notched isot impact strength of 10 Kg·cm/cm ² is within the range of the inequality defined in the claims. Comparative example 7 Melt index 3g/10 minutes PP resin 35g,
Phlogopite powder 35 with weight average aspect ratio 10 or 67
g and 0.4 g of tolylene diisocyanate were melt-mixed in a Brabender Plastograph at 200°C and a rotor rotation speed of 20 rpm. Feed the resulting mixture to an extruder,
Made pellets. Using the obtained pellets, injection molding was performed in the same manner as in Example 1, and the Izo impact strength and warpage were measured in the same manner as in Example 1. The tensile strength was also measured. those results first
Shown in the table.

[Table] As is clear from Table 1, the composition of this comparative example did not yield a molded article having an Izot impact strength that would not cause any problems in practical use. Comparative Example 8 Using pellets produced using exactly the same composition and method as in Example 1 and Comparative Example 1, test pieces were produced by press molding. During press molding, the pellets are pressed in advance into a sheet with a thickness of approximately 0.5 mm using a press molding machine kept at 220°C, and then 15 sheets are stacked and charged into the mold again. A test piece of 200 x 100 x 6 mm was prepared by press molding at a temperature of 220°C. In addition, when press forming, use the mold in which the sample was charged.
After pressing at a temperature of 220°C, the mold was transferred to a cooling press through which water was passed, and after the mold was cooled to 60°C, the test piece was released from the mold. The obtained rectangular plate-shaped test piece of 200 x 100 x 6 mm was left in a constant temperature and humidity room at 23°C and 65% RH for 48 hours, and the warpage was measured using the method shown in Figure 8. It is expressed as: size=hmax−sample thickness/d×100. (d represents the length of the sample piece: 200 mm.) In addition, the unnotched Izot impact strength was measured by cutting a test piece prepared by press molding into a shape of 13 x 64 x 6 mm. FIG. 9 shows a summary of the results of warping and non-notched isot impact strength measured by the above method using a press-formed plate. Compared to the results shown in Figure 2 when the same pellets were made into test pieces by injection molding, the warpage of the molded product was smaller across the board, while the non-notched isot impact strength was lower, especially in the region with a low mica content. It became a low value. As mentioned above, the characteristics of the composition of the present patent in terms of warp/isot impact strength are only realized when molded articles are produced by injection molding.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for measuring the warpage of a sample piece for physical property evaluation molded using the molding resin composition of the present invention, where d is the diameter of the sample disk, and hmax is the warpage measured on a horizontal plate. Indicates the maximum warping height of the disc when FIG. 8 is a diagram showing a method for measuring the warpage of a sample piece for physical property evaluation obtained from the resin composition of the present invention by press molding, where d indicates the length of the sample piece, and 1 indicates the weight. , and hmax indicates the maximum warping height of the sample piece when placed on a horizontal plate. Figures 2 to 7 and 9 show the unnotched isot impact strength (Kg・cm/cm ² ) of individual samples in relation to the mica powder mixing ratio (wt%) and the aspect ratio of mica in the composition. The measurement result of warpage (%) is entered, and the warpage (%) is shown in parentheses at the top.
, the lower row ( ) shows the impact strength without notch, Figure 2 shows the results for Example 1 and Comparative Example 1, Figure 3 shows the results for Example 2 and Comparative Example 2, and Figure 4 shows the results for Example 2 and Comparative Example 2. 5 shows the results obtained for Comparative Example 3, FIG. 5 shows the results obtained for Comparative Example 4, FIG. 6 shows the results obtained for Comparative Example 5, FIG. 7 shows the results obtained for Example 6 and Comparative Example 6, and FIG. 9 shows the results obtained for Comparative Example 8. In each figure, ● indicates a case where both warpage and impact strength are satisfied, and 0 indicates a case where either or both of warpage and impact strength are not satisfied.

Claims (1)

[Claims] 1. (a) a crystalline aliphatic polyolefin resin with a melt index of 4 to 20 g/10 min, (b) a mica powder with a weight average aspect ratio of 5 or more, and (c) an interface between the resin and the mica powder. The composition contains an additive that imparts chemical bonding or affinity as an essential component, and the weight average aspect ratio A of the mica powder contained in the composition and the mica powder mixing ratio B weight % are −1.0A+35≦B≦ -0.25A+50 (5≦A≦20) ...(1) -0.2A+19≦B≦-0.25A+50 (20<A) ...(2) A flat injection molded product.