JPH0232982B2 - SEKISOTAINOSUTANPINGUSEIKEIHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for stamping a laminate. In general, thin material forming methods such as vacuum forming and stamping molding require shorter processing time than injection molding, and the strength of the molded product is superior because no welds are observed. However, in order to provide more functions such as vibration damping and soundproofing, vacuum forming or stamping is performed using a laminated sheet consisting of layers of materials with different heat deformation temperatures. It does not have enough strength and is likely to peel off during molding. Particularly in vacuum forming, when the heat deformation temperatures of the sheet materials are different, uneven thickness may occur before forming or during heating, or if the heat deformation temperatures of the two are extremely different, the lower melting point layer may be located below. Sometimes the material drips. For this reason, the range of material selection is limited in the combination of materials in laminated sheets having different heat distortion temperatures. Particularly in thick materials, such materials often cause problems during thermal deformation, such as sagging or floating of the sheet during heating or peeling during drawing, which tends to limit the forming of laminated sheets. In view of the above circumstances, it is an object of the present invention to provide a molding method that does not cause dripping, uneven thickness, or peeling of materials even when materials with different heat distortion temperatures are stamped. The gist is a stamping molding method characterized by heating a plurality of sheets, each having a different heat deformation temperature, separately and then pressing them together. In the present invention, not only a two-layer molded product but also a multi-layer structure of three or more layers can be made, and since it is only necessary to overlap different types of sheets in functionally necessary parts, it is possible to create molded products with different layers, such as vacuum forming. Molding using a uniform two-layer sheet not only allows for the production of molded products that cannot be imitated, but is also functionally superior and economical. Furthermore, two or more types of materials may be stacked alternately, and it is also possible to partially build up the material. In this way, the sandwich structure can be easily formed, and a mechanically superior structure can be obtained, making it possible to create ribs or injection molded products with large thickness changes, which could not be achieved with conventional vacuum forming or stamping molding. It has become possible to mold similar molded products. In addition, according to this method, the sheets are heated separately in advance and crimped at the same time as forming, so depending on the combination of sheet area size, it is less likely that the other sheet material will mix into the recycled material during trimming. There is very little loss of material properties. As described above, it has superior formability compared to multilayer sheets for vacuum forming products, and it is easy to form overlay molded products, making it possible to form multilayers using two or more different materials only in functionally required areas. It is characterized by the fact that it can be used as a laminated material or a composite material and can be combined in a wide variety of ways to suit the required functions of the molded product by taking advantage of the material's properties. Any material may be used as long as it is suitable as a stamping molding material, but preferably a polyolefin material and a mixture of materials having different heat distortion temperatures are preferred. Note that stamping molded materials undergo plastic working at a relatively low temperature, below their melting point, so if the heat deformation temperatures of two types of sheet materials are significantly different, one must be heated to a lower temperature for handling and heat resistance reasons. In order to obtain uniform and good adhesion when the materials are overlapped and pressed together, it is desirable that the heat deformation temperatures be close to each other. By the way, maleic anhydride-grafted polypropylene among modified polypropylenes plays a major role in adhesion, and to further increase adhesive strength, it is necessary to use a material that has polar groups and has a lower heat distortion temperature than maleic anhydride-grafted polypropylene. When used together, great synergistic effects can be achieved. The material with a high heat distortion temperature is usually a stamping material with high rigidity and a flexural modulus of 10,000 Kg/cm ² or more, and is preferably a blend of high-density polyethylene and polypropylene, and the heat distortion temperature, stiffness, etc. are determined by the blend ratio. can be adjusted. On the other hand, materials with a low heat distortion temperature usually have low rigidity and exhibit functions such as vibration damping and sound insulation, but they are blends made of polypropylene, maleic anhydride graft-modified polyethylene, and ethylene propylene diene copolymer, and the blend ratio is The heat deformation temperature, rigidity, adhesion strength, etc. can be adjusted. In addition, when using ethylene-vinyl acetate copolymer in combination with materials with low heat distortion temperatures, the temperature during melt blending can be lowered, and if unreacted maleic anhydride is present, the double bonds are left behind and bonding occurs during pressure bonding. In addition, since it has a polar group of carboxylic acid, it lowers the surface energy and creates a unique environment on solid surfaces, so when used in combination with maleic anhydride graft-modified polyolefin, there is a significant increase in adhesive strength. It is thought that the improvement is recognized. The present invention will be further explained below by giving Examples and Comparative Examples. In the example, MFR means melt flow rate (g/10min), HLMFR means high load melt flow rate (g/10min), and the heat distortion temperature is
Per ASTM D648 (66psi). Example 1 (a) A material with a high heat distortion temperature is a blend of polypropylene (MFR ₂₃₀ ℃ = 1.5) and medium density polyethylene (MFR ₁₉₀ ℃ = 0.25) at a blend ratio of 50 wt%/
230 in a continuous mixer after dry blending at 50wt%
Blended at ℃, heat distortion temperature is 90
℃, and this material was used to make a 1.5 mm thick sheet material. (b) Ethylene propylene block copolymer (MFR ₂₃₀ ℃ = 4.0) is a material with a low heat distortion temperature.
Amorphous ethylene propylene diene copolymer (HLMFR ₂₃₀ ℃ = 0.4, propylene content in rubber = 35 wt%, rubber concentration = 61 wt%) and maleic anhydride graft modified polypropylene homopolymer at 44 wt% / 36 wt% / 20 wt% Dry blending was performed in advance in a tumbler at the blending ratio.
At this time, 0.05 parts by weight of an antioxidant (trade name: BHT) was added to the blend resin. Blending was carried out using a 20% continuous mixer using steam while adjusting the jacket temperature of the mixer to 220-230°C. The heat distortion temperature of the obtained material is 68℃, and using this material
A sheet material with a thickness of 1.5 mm was used. The two types of sheet materials made in this way are heated in contact with a hot plate so that the surface temperature of the resin with a high heat distortion temperature is 150℃, and the surface temperature of the resin with a low heat distortion temperature is 130℃. Back side) Align the comrades and cut 0.2 from the thickness of the two sheets to avoid cutting.
The peel strength was measured by pressing a spacer as small as 1 mm in between at a low pressure of 5 to 10 kg/cm ² . On the other hand, the sheets were preheated under the same conditions as above using a mold capable of forming the shape shown in Figure 1, and the stacked sheets were stamped and formed. A part of the molded product was sampled by punching and the peel strength was measured, but none of the samples were peeled from the adhesive surface and the test piece yielded and broke. The evaluation method was to measure peel strength using a test method based on ASTM D952-51. In Figure 1, a: 500mm, b: 300mm, c: 3mm
φ, d: 50mm, e: 80mm, f: 100mmφ, g: 130
mmφ, h: 100mm, i: 50mm, j: 70mm, k: 1.3
Dimensions in mm are shown. Comparative Example 1 Amorphous ethylene-propylene diene copolymer (heat distortion temperature 40
°C) in the same manner except that it was used alone and was not preheated.
Pressure bonding was carried out at 130°C, but the material peeled off with an extremely low peeling load, so it could not be considered adhesion, and sheet heating temperatures of 170°C or higher were required to prepare material test pieces for peel tests. Comparative Example 2 The ethylene propylene block copolymer used in the material with a high heat distortion temperature described in Example 1 and the material with a low heat distortion temperature in the same example and the ethylene propylene diene copolymer used in Comparative Example 1 were combined. blend ratio
Blend of 70wt%/30wt% (heat distortion temperature
A peeling test was carried out using the same evaluation method as in Comparative Example 1, but peeling occurred at an extremely low value.To prepare this sample, the pressure contact temperature was 170℃.
℃ or higher was necessary. Example 2 Example 1 as a blend material with low heat distortion temperature
Ethylene propylene block copolymer used in
In addition to ethylene propylene diene copolymer and maleic anhydride graft modified polypropylene, ethylene vinyl acetate copolymer (MFR ₁₉₀ ℃ = 2.0, density =
0.932g/cm ³ , vinyl acetate content 15wt%) at a blend ratio of 44wt%/36wt%/1.5wt%/5wt%, and an antioxidant (trade name BHT) relative to the resin amount.
After adding 0.05 parts by weight and dry blending using a tumbler, blending was performed at 210 to 220°C using a twin-screw continuous mixer. The heat distortion temperature of the obtained material was 66°C, and a sheet with a thickness of 1.5 mm was made using this material. When a peel test was conducted in the same manner as in Example 1 using the sheet of the material with a high heat distortion temperature used in Example 1 as a base material to be adhered, it was found that the surface temperature of the resin with a high heat distortion temperature described in Example 1 was 135℃, 15℃ lower than 150℃, lower deformation temperature resin surface temperature 130℃
By using maleic anhydride graft-modified polypropylene and ethylene-vinyl acetate copolymer in combination, the minimum temperature required to maintain adhesion can be significantly lowered, and a synergistic effect was observed to increase the adhesion strength. . Comparative Example 3 As a material with a low heat distortion temperature, a blend system consisting of the same material as in Example 2 but with the maleic anhydride graft modified polypropylene removed, was made of ethylene propylene block copolymer, ethylene propylene diene copolymer, and ethylene. Vinyl acetate copolymer blend ratio 44wt%/36wt%/20wt
A peel test was carried out in the same manner as in Comparative Example 1, except that a blend of 50% and 100% (heat deformation temperature: 80°C) was used, but sufficient adhesion was not observed even when the temperature was raised to 170°C. It was necessary. Examples 3 to 4 In Example 2, the blend ratio of (ethylene propylene block copolymer)/(ethylene propylene diene copolymer) among the materials with low heat distortion temperature was kept constant at 9:11, and maleic anhydride grafting was performed. Example 3 shows the results of changing the absolute amount of modified polypropylene + ethylene vinyl acetate copolymer within 20 wt%.
4. Comparative Examples 4 to 6 The ethylene vinyl acetate copolymer used in Example 2 as a material with a low heat distortion temperature, the high-pressure low density polyethylene, ( Density: 0.920
g/cm ³ , MFR ₁₉₀ ℃ = 2) Low-pressure method Low-density polyethylene (density: 0.920 g/cm ³ , MFR ₁₉₀ ℃ = 0.2) was crimped alone, and the temperature was raised to near the melting point of the material with a low heat distortion temperature. However, sufficient adhesive strength could not be obtained, and even if the temperature was raised even higher to 170°C, the adhesive strength did not improve, requiring a temperature of 175°C or higher. Example 5 Among the materials described in Example 1, the blend ratio of ethylene propylene block copolymer and amorphous ethylene propylene diene copolymer, which are materials with a low heat distortion temperature, was kept constant at 9:11, and maleic anhydride graft modification was carried out. Although the amount of polypropylene was reduced to 5wt%, there was almost no change in bonding temperature or strength. Table 1 summarizes the above results. In addition, A in the table is an ethylene propylene block copolymer,
B is an amorphous ethylene propylene diene copolymer,
C represents maleic anhydride graft-modified polypropylene, and D represents ethylene-vinyl acetate copolymer.

[Table] However, the peel strength of the comparative example is the value at the lowest temperature at which bonding is possible.

[Brief explanation of drawings]

Figures 1, a and b show the shape of the stamped test piece, where a is a plan view and b is a -
It is a line view.

Claims (1)

[Claims] 1. A method for stamping and forming a laminate, which comprises separately heating a plurality of sheets made of materials having different heat distortion temperatures and then pressing them together.