JPS626503B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to anti-slip polypropylene molded articles. Specifically, the present invention relates to a polypropylene molded product equipped with an anti-slip material that has an excellent anti-slip effect and good durability. Polyolefin molded products such as polypropylene have excellent water resistance and chemical resistance, are hygienic, and have uniform specifications for molded products, so they have come to be widely used in place of wood, metal, etc. However, although this polyolefin molded product has the above-mentioned excellent features, it also has the drawback of being slippery. Particularly when pallets used for transporting or storing cargo are made from polyolefin molded products, slipping may occur between the cargo and the pallet, between the pallet and fork such as a forklift, or between pallets. There is a risk of the cargo collapsing when transporting or transferring the cargo. Conventionally, methods to prevent the above-mentioned slipping have been used, such as creating irregularities on the surface of molded products such as pallets, or fitting rubber anti-slip fittings, but these methods have various problems. It's hard to say that I'm still satisfied with it. The inventors of the present invention have conducted intensive studies in order to eliminate the above-mentioned drawback of conventional polypropylene molded products being easy to slip.As a result, the inventors have developed a method for attaching an anti-slip material made of a special composition to a polypropylene molded product in a specific configuration. They discovered that the problem could be solved by doing this and completed the present invention. That is, the gist of the present invention is to mold an anti-slip material formed by molding a blend of ethylene propylene diene rubber and high-pressure low density polyethylene having long chain branches in a weight ratio of 20:80 to 80:20 into a polypropylene molded product. It consists of polypropylene molded products made by heat welding. Hereinafter, an example of the molded product of the present invention will be further explained using the drawings. FIG. 1 is a perspective view of a pallet which is an example of the molded product of the present invention. In the figure, 1 indicates a molded product (pallet), and 2 indicates a non-slip material. The synthetic resin constituting the molded product (pallet) 1 of the present invention is selected from consideration of thermal weldability with the anti-slip material 2, etc.
A polypropylene resin is used, and among them, one having a hardness (hardness according to JIS K6301) of JIS A97 or higher and close to 100 is preferable. To put this more simply, a hard polyolefin containing polypropylene as a main component and having a Shore hardness (hardness according to ASTM D 2240 Shore D) of 60 or more, preferably 70 or more is preferred. The polypropylene constituting the molded article 1 described above contains antioxidants, ultraviolet absorbers, heat stabilizers, antistatic agents, flame retardants, crosslinking agents, blowing agents, dyes, pigments,
Additives such as organic fillers and inorganic fillers may be added and mixed, and the molded product 1 may be molded by conventional molding methods such as injection molding, extrusion molding, cast molding, etc. depending on the desired molded product. Used arbitrarily. When the molded product 1 is a pallet, it is desirable to add a foaming agent to the above-mentioned polypropylene to obtain a low-foaming injection molded product having a non-foamed layer on the surface layer at an expansion ratio of about 1.05 to 1.5 times. Of course, it may be non-foamed. The anti-slip material 2 is obtained by molding a blend of ethylene propylene diene rubber and high pressure low density polyethylene having long chain branches. Ethylene propylene diene rubber is a rubbery product obtained by polymerizing, for example, ethylene, propylene, and diene in the presence of a Ziegler catalyst, etc. The diene component as an unsaturated component includes dicyclopentadiene, ethylidene norbornene, and methylene norbornene. Bohnen, 1,4-hexadiene, and the like. This ethylene propylene diene rubber preferably contains 60 to 80% by weight, preferably 70 to 80% by weight of ethylene component. Furthermore, high-pressure low-density polyethylene having long chain branches is obtained by polymerizing ethylene alone or a mixture of ethylene and a small amount of a copolymer component using a high-pressure method, and has a density of 0.94 or less, preferably 0.925.
These are as follows. Also, the melt index (190℃) is 0.1 to 2.5.
g/10 minutes is preferred. Examples of the copolymerization component include vinyl acetate, ethyl acrylate, methyl methacrylate, diethyl maleate, etc., and the proportion thereof is 10% by weight or less. The above-mentioned high-pressure low-density polyethylene is different from linear low-density polyethylene developed in recent years, and has a molecular structure having many long chain branches in the molecule. A long chain branch is one having a much larger number of carbon atoms than a short chain branch, which is about 2 to 6 carbon atoms. Comparing the physical properties of high-pressure low-density polyethylene with long chain branches and linear low-density polyethylene,
The difference is clearly revealed by the viscosity average molecular weight,
Taking a melt index of 2 as an example, high-pressure low density polyethylene having long chain branches has a value of 50,000 or less, and is about 30,000 to 40,000, and linear low density polyethylene has a value of about 70,000 to 80,000. The anti-slip material 2 is made of a blend of ethylene propylene diene rubber and high-pressure low density polyethylene having long chain branches as described above, and the blending ratio is 20 to 80% by weight of ethylene propylene diene rubber, preferably 30 to 80% by weight. 70% by weight, preferably 40~
60% by weight, high-pressure low density polyethylene having long chain branching accounts for 80-20% by weight, preferably 70-30% by weight, more preferably 60-40% by weight. Of course, the above-mentioned additives may be further added to this mixture. In addition to the above ethylene propylene diene rubber and high-pressure low density polyethylene having long chain branches, other thermoplastic synthetic resins are added to these mixtures in an amount that does not exceed the amount of each of the above two components. Also good. As other thermoplastic synthetic resins, polyolefin resins are preferred. Furthermore, a part of the above ethylene propylene diene rubber may be mixed with ethylene propylene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, polybutadiene rubber, polyisoprene rubber, polychloroprene rubber, polyurethane rubber, within a range not exceeding the blending amount of ethylene propylene diene rubber. It may be replaced with other synthetic rubbers such as , thiocol rubber, etc. The anti-slip material 2 is formed from the above-mentioned mixture into a desired shape such as a band, a string, a plate, a block, etc. by extrusion molding, injection molding, or other suitable molding means. The anti-slip material 2 should have a hardness (according to JIS K6301) of JIS A75 to JIS A95 and a tensile strength {JIS
Strength by K6758-81 (at constant temperature of 20℃)} is 50
~250Kg/ ^cm2 is desirable. Heat welding is used to install the anti-slip material 2 on the molded product 1. For example, if the surface of the molded product 1 and the surface of the non-slip material 2 are melted using hot air or a hot plate, both of them are still molten. Crimp while in the state,
A method of joining the two, when molding the molded product 1 by injection molding etc., the anti-slip material 2 is placed at the required position in the mold.
is fixed, molten polypropylene is filled into the mold, and the melting heat is used to thermally weld the molded product 1 and the anti-slip material 2. , a method is used in which the material is extruded into a string shape or the like, and then pressed and welded to the surface of the molded product 1 (which may be preheated, oxidized, etc., to improve adhesion). Usually, a method is used in which a non-slip material 2 is placed near a molded product 1, and hot air is blown onto both to melt the surface of the molded product 1 and the surface of the non-slip material 2, and the two are crimped and welded. It will be done. The welding conditions for this welding method are the temperature of the hot air,
Although it cannot be definitively determined as it varies depending on the amount of hot air, the distance from the hot air outlet to the molded product 1 and the anti-slip material 2, etc., if we take a line speed of about 1 m/min as an example, it will be 600 to 800°C. Blow hot air (temperature of the heater in the hot air generator) to the surface of the molded product 1 and the surface of the anti-slip material 2 to form a molten layer on the surface of the molded product 1 and the surface of the non-slip material 2,
This is done by pressing the molten parts together with a pressure roller or the like at a pressure of about 0.5 kg/cm or more while the surfaces of both are in a molten state. Next, the characteristics of the molded article of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Various physical properties described in the examples were measured by the following measurement methods. (1) Melt index: Compliant with JIS K6760-81
Measured at a constant temperature of 20°C. (2) Density: Same as above.(3) Tensile strength: Same as above.(4) Elongation: Same as above. Using a test piece, peel approximately half of the anti-slip material from the base material in the length direction, and then remove the peeled anti-slip material from the base material.
The anti-slip material and one end of the base material were fixed to the chuck of the testing machine with the material folded back 180 degrees, and the anti-slip material was peeled from the base material at a constant speed of 50 mm/min at a constant temperature of 20°C. The force was read and the average value was expressed in Kg/cm. (6) Sliding angle: 2mm thick, length and width on the surface plate
A 250 mm anti-slip material sheet was attached, and a sheet made of polyethylene or polypropylene with a thickness of 2 mm and a length and width of 80 mm was placed thereon, and a load of 1 kg was applied to the sheet. From this state, one side of the surface plate was pulled up at a constant speed of 100 mm/min, and the angle at which the placed sheet started to slide (angle with respect to the horizontal plane) was measured, and the average value of three measurements was calculated. (7) Hardness: Measured at a constant temperature of 20°C in accordance with JIS K6301-81A method. (8) Wear rate: Using a custom fabric abrasion tester manufactured by Daiei Kagaku Co., Ltd., No. 40 sandpaper was brought into contact with a non-slip material measuring 35 mm in length, 20 mm in width, and 2 mm in thickness.
A load of 3.4 Kg (7.5 1b) was applied, and the anti-slip material was subjected to reciprocating motion at a constant temperature of 20°C with a stroke of 50 mm, repeated 5000 times to wear out the anti-slip material, and the amount of wear was expressed as a weight percentage of the original weight of the anti-slip material. In the table of Examples, ethylene propylene diene rubber is referred to as "EPDM", ethylene homopolymer of high-pressure low density polyethylene with long chain branching is referred to as "HPLD", and ethylene-vinyl acetate copolymer is referred to as "EVA". ” was abbreviated as “. Examples 1 to 3 Ethylene propylene diene rubber (EPDM) (manufactured by Japan EP Rubber Co., Ltd., ethylene propylene terpolymer EP57T, ethylene content 67% by weight) and high-pressure low density polyethylene with long chain branching (ethylene homopolymer) ) (HPLD) {Mitsubishi Chemical Industries, Ltd.
manufactured by Novatec F100, Melt Index (190
℃): 0.42 g/10 minutes, density: 092 g/cm ³ } in the proportions shown in Table 1 below, and extruder {Tanabe Plastic Machinery, VS30-22 type extruder, tip Dalmage type
30φ, L/D: 22, compression ratio: 3.5} to make pellets, and then press molding to create a sheet with a thickness of 2 mm, length and width of 250 mm, and this was used as an anti-slip material. Polypropylene {manufactured by Mitsubishi Yuka Co., Ltd., Mitsubishi Norvenon BC-8, melt index (230℃): 1.2
g/10 minutes, density: 0.9 g/cm ³ } onto a plate with a thickness of 3.5 mm and a length and width of 250 mm, and the above anti-slip material sheet was applied at 230°C for 5 minutes at 4 kg/cm ² Heat welding was carried out by press molding under pressure conditions. Table 1 shows various physical properties of the obtained anti-slip material. Examples 4 and 5 The anti-slip material was heated in the same manner as in Example 1, except that HPLD was replaced with ethylene-vinyl acetate copolymer (manufactured by Sumitomo Chemical Co., Ltd., Evatate D2011, vinyl acetate content 5% by weight). A welded molded product was obtained. Table 1 shows various physical properties of the obtained anti-slip material. Comparative Examples 1 to 4 Slips created using the ethylene propylene diene rubber or HPLD used in the examples, ethylene propylene diene rubber alone, HPLD alone, or a blend of ethylene propylene diene rubber and HPLD outside the scope of the present invention. The anti-slip material was treated in the same manner as in Example 1 to obtain a molded product with the anti-slip material thermally welded. Table 1 shows various physical properties of the obtained anti-slip material. Example 6 The pellets of Example 1 were used to make a strip sheet with a thickness of 2 mm, width of 20 mm, and length of 1 m using an extruder, and the strip sheet was manufactured using the same polypropylene as used in Example 1 as an anti-slip material. A structure similar to that shown in FIG. 1 was heat welded to the surface of the pallet. Thermal welding is performed by melting the anti-slip material and the surface of the pallet using hot air at a temperature of 700 to 800℃ (built-in heater temperature) and a flow rate of 120/min, and pressing both together with a pressing force (roller linear pressure) of 2 kg/cm. I did it. The anti-slip material adhered well to the pallet, and its anti-slip properties were sufficient for practical use.

[Table] The polypropylene molded product to which the anti-slip material of the present invention is attached has good anti-slip properties between it and the articles placed on the pallet, for example, when this molded product is used as a pallet for transporting cargo. In addition, it is excellent in wear rate, welding strength, etc., and is very preferable for practical use.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a pallet which is an example of the molded product of the present invention. In the figure, 1 indicates a molded product (pallet), and 2 indicates a non-slip material.

Claims (1)

[Claims] 1. Weight ratio of ethylene propylene diene rubber to high pressure low density polyethylene having long chain branches: 20:
A non-slip polypropylene molded product made by thermally welding a non-slip material made from an 80 to 80:20 mixture to a polypropylene molded product. 2. Claim 1, characterized in that the ethylene propylene diene rubber contains 54 to 80% by weight of an ethylene component, 18 to 40% by weight of a propylene component, and 1 to 10% by weight of a diene component. The polypropylene molded product described in . 3. The method according to claim 1 or 2, characterized in that an ethylene-vinyl acetate copolymer copolymerized with 10% by weight or less of vinyl acetate is used as the high-pressure low-density polyethylene having long chain branches. Polypropylene molded product.