JPH10338231A - Pallet made of polyolefin resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability, and at the same time, increase the antislip effect at high and low temperatures by a method wherein an antislip material is heat-welded on a pallet main body constituted by forming a polyolefin resin, and the antislip material is formed of a composition of which the major component is a polyolefin resin with a dispersion degree of a specified value or lower. SOLUTION: When an antislip material is provided on a pallet made of polyolefin by heat-welding, as the antislip material, a polyolefin based resin (low dispersion degree polyolefin based resin), of which the ratio of a molecular weight distribution (dispersion degree), which is specified by Mw (weight mean molecular weight)/Mn (numeral mean molecular weight), is 4 or lower, preferably, 3 or lower, is used. This low dispersion degree polyolefin based resin is obtained by using a so-called metallocene catalyst (it is called a Kaminsky catalyst or a single site catalyst) as the polymerization catalyst, and as such a low dispersion degree polyolefin based resin, a polyethylene resin and a polypropylene resin can be counted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin pallet. More specifically, the present invention relates to a polyolefin resin pallet with a non-slip material, which has an excellent non-slip effect and durability, and particularly exhibits a stable non-slip effect when used at high and low temperatures.

[0002]

2. Description of the Related Art Polyolefin molded products such as polypropylene and polyethylene are excellent in water resistance, chemical resistance, etc., are sanitary, and are frequently used in place of wood, metal, etc. in terms of constant specifications of molded products. It was started. However, this polyolefin molded article has the above-mentioned excellent features, but has the disadvantage that it is slippery. In particular, when a pallet is used to carry or store luggage with this polyolefin molded product,
Slippage is likely to occur between a load and a pallet, between a pallet and a fork such as a forklift, between pallets, and the like, and there is a risk of collapse of the load when carrying or transferring the load.

[0003] Conventionally, various methods have been used to prevent the slippage as described above. For example, a non-slip material having a specific composition is made of polypropylene,
It has been proposed to attach to a molded product of polyolefin such as polyethylene (JP-A-58-102723, JP-A-58-102724, JP-A-61-1).
No. 23532).

[0004]

The non-slip material mounted on the pallet described above exhibits a sufficient anti-slip effect when used at room temperature, but is heat-treated with the product placed on the pallet. When it is necessary, or when used in high or low temperatures such as loading or unloading into or out of the refrigerator, the anti-slip material may soften or become too hard and the anti-slip effect may not be fully exhibited. there were. The present inventors have conducted intensive studies to solve such a problem, and as a result, have found that the above-mentioned problem can be solved by providing a non-slip material of a special material on a polyolefin resin pallet by welding. The invention has been completed.

[0005]

The gist of the present invention is a polyolefin resin pallet in which a non-slip material is provided on a pallet body formed by molding a polyolefin resin by heat welding, wherein the non-slip material is Mw (weight). Average molecular weight) / Mn
A polyolefin resin pallet characterized by being composed of a composition containing a polyolefin resin having a degree of dispersion defined by (number average molecular weight) of 4 or less as a main component.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyolefin resin pallet of the present invention uses a special polyolefin resin as a non-slip material. In the present invention, the anti-slip material includes Mw
A polyolefin resin having a ratio (dispersion degree) of molecular weight distribution defined by (weight average molecular weight) / Mn (number average molecular weight) of 4 or less (preferably 3 or less) (hereinafter abbreviated as low-dispersion polyolefin resin). ) Must be used.
By using such a specific polyolefin-based resin, it is possible to satisfy the specific performance of being excellent in durability and stably exhibiting a non-slip effect when used at high and low temperatures.

[0007] The low-dispersion polyolefin resin is usually
It is a very homogeneous polymer obtained by using a so-called metallocene catalyst (also called a Kamansky catalyst or a single-site catalyst) as a polymerization catalyst and having a very sharp molecular weight distribution and a very sharp composition distribution. The degree of dispersion can be determined by measuring Mw and Mn by a universal calibration method, that is, a GPC method using polystyrene having a known molecular weight as a standard substance.

The low-dispersion polyolefin resins include:
A typical example is a polyethylene resin and a polypropylene resin. These polyolefin resins may be homopolymers or copolymers with other α-olefins. As other α-olefin, in the case of polyethylene resin, propylene, butene-1, 4-methylpentene-1, hexene-1, octene-1 and the like are used, and in the case of polypropylene resin, ethylene, butene-1 and the like are used. Typically used.

For example, it is a copolymer of 20 to 90% by weight of ethylene and 80 to 10% by weight of an α-olefin having 3 to 12 carbon atoms. Examples of the α-olefin having 3 to 12 carbon atoms include propylene. , Butene-1, penten-
1, hexene-1, 4-methyl-pentene-1, octene-1 and the like. When the α-olefin content is too high, a rubbery substance having tackiness is obtained.
-If the olefin content is too low, the adhesion tends to decrease.

The ethylene-α-olefin copolymer resin having a low degree of dispersion has the above-mentioned ethylene and α-olefin having 3 to 12 carbon atoms.
-It is produced by a metallocene catalyst or the like using an olefin. The metallocene catalyst is a transition metal (F
e, Ti, Zr, Hf, etc.) are sandwiched between unsaturated cyclic compounds, enabling precise control of stereoregularity, molecular weight, copolymerizability, and the like.

A conventional Ziegler-Natta type catalyst or the like is called a multi-site catalyst (MSC) because active sites having different properties are mixed, and low molecular weight components other than the target molecular weight are simultaneously generated. On the other hand, metallocene catalysts are called single-site catalysts (SSCs) because their catalytic active sites are uniform. A homopolymer having a narrow molecular weight distribution can be obtained, and a molecular weight distribution related to processability and a composition distribution related to product properties. Can be arbitrarily controlled.

The low-dispersion polyolefin-based resin may be polymerized using two or more metallocene catalysts. Such a polyolefin resin has a molecular weight, MF
It has bimodal or multimodal characteristics, such as a blend of different polyolefin resins such as R. And
The MFR of the low-dispersion polyolefin resin is usually 2 to 1
50 g / 10 min (2.16 kg, 190 ° C.)
In the present invention, the MFR is not particularly limited. Further, the density of the low-dispersion polyolefin resin is usually 0.87 to
0.94 g / cm ³ .

It is not necessary to use the low-dispersion polyolefin resin alone for the purpose of improving the extrudability, etc., but to use it by blending it with another polyolefin resin obtained using a usual polymerization catalyst. You can do it. in this case,
The content of the low-dispersion polyolefin resin in the blend is at least 50% by weight, preferably at least 80% by weight. Other polyolefin resins include, for example, polyethylene, polypropylene, copolymers of propylene and other α-olefins, VLPE, LLDP
E or the like can be used.

As a non-slip material, generally a thickness of several mm,
It is provided by molding into a tape having a width of several centimeters and welding in grooves provided in the vertical and horizontal directions on the pallet surface. Extrusion molding is usually used to mold the non-slip material into a tape. In this case, LDPE having a density of about 0.91 to 0.93 g / cm ^{3 is} added to the low polydispersity polyolefin for 20 to
When about 50% by weight is mixed, the extrudability is improved, and a highly efficient and uniform tape-shaped non-slip material can be obtained.

In order to further improve moldability and durability, a heat stabilizer such as a phenol-based, thioether-based, phosphorus-based, or fatty acid metal salt is used in an amount of 0.01 to 100 parts by weight of the low polydispersity polyolefin-based resin. About 0.5 parts by weight, benzotriazole (trade name Tinuvin 326, manufactured by Nippon Ciba Geigy Co., Ltd.), etc., and Sanol LS-770 (trade name)
It is preferable to use about 0.01 to 1.0 part by weight of a light stabilizer such as (manufactured by Sankyo Co., Ltd.).

The anti-slip material is melted by blowing hot air or the like onto the surface of the pallet body and the surface of the anti-slip material, and the two are pressed and welded. The material is desirably the same type of polyolefin resin. That is, from the viewpoint of adhesiveness, it is preferable to use a polyethylene non-slip material for a polyethylene pallet body and to use a polypropylene non-slip material for a polypropylene pallet body. Further, in order to improve the adhesiveness between the pallet body and the non-slip material, a modified polyolefin may be mixed in the non-slip material.

The modified polyolefin is obtained by grafting a part or all of the polyolefin with an unsaturated carboxylic acid or a derivative thereof. For example, a radical generator such as a polyolefin, an acid monomer and an organic peroxide may be melt-kneaded by a solution kneading method. It is obtained by performing a graft reaction by various methods such as a graft method and a slurry graft method. The polyolefin used for the modified polyolefin is an ethylene polymer, a propylene polymer, an ethylene propylene copolymer, an ethylene-vinyl acetate copolymer, an ethylene butene 1 copolymer, and other olefin copolymers alone or as a mixture. used.

The unsaturated carboxylic acids and derivatives thereof include acrylic acid, maleic acid, fumaric acid, maleic anhydride,
Endo-bicyclo- [2,2,1] -5-heptene-
2,3-dicarboxylic anhydride and the like. Among them, maleic anhydride is preferred. Also, a mixture of these can be used. Usually, the amount of the unsaturated carboxylic acid or the like to be used is 0.1 to the obtained modified polyolefin.
01 to 3%, particularly preferably 0.05 to 1%.

The amount of the modified polyolefin added is such that the amount of unsaturated carboxylic acid or anhydride thereof in the anti-slip material is 10 to 10;
000 ppm, preferably about 50 to 5,000 ppm. The anti-slip material has a hardness (hardness according to JIS K6301) of JIS A75 in terms of anti-slip properties, welding properties, compressive deformation, wear resistance, and the like.
~ JIS A95, tensile strength ｛JIS K6758-8
Strength at 1 (at 20 ° C constant temperature)｝ is 50-250k
g / cm ² . The hardness may be adjusted by selecting the molecular weight of the low-dispersion polyolefin, selecting a copolymer monomer, or mixing the other polyolefin resin described above.

[0020]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 75 parts by weight of an ethylene-hexene-1 copolymer having a dispersity of 3.5 produced by a metallocene catalyst and low-density polyethylene (MI: 1.9 g / 10 min, density: 0.92 g / c)
m ³ ) 25 parts by weight were mixed and 2 mm thick by an extruder.
A tape having a width of 20 mm was prepared and used as a non-slip material.

Hardness of non-slip material (JIS K6301)
Was JIS A92. The obtained non-slip material was treated with polyethylene (MI: 5.0 g / 10 min, density 0.96 g /
6 pieces were welded to the surface of the pallet made of cm ³ ) along the longitudinal direction of the pallet. Welding 700 ~
Hot air heated to 800 ° C. was simultaneously blown onto the non-slip material and the pallet surface to melt the surface and press it.

The 180 ° peel strength is 6 kg / cm, and the slip angles are 28 ° (20 ° C.), 29 ° (40 ° C.), 25 ° (−
10 ° C.). The measuring method is as follows. 180
° Peel strength: about 250 mm long test piece obtained by welding a non-slip material having a width of 20 mm and a thickness of 2 mm to a base material, and peeling off about half of the non-slip material from the base material in the length direction of the non-slip material;
One end of the anti-slip material and one end of the base material are fixed to the chuck of the testing machine in a state where the separated anti-slip material is folded back by 180 °, and
The anti-slip material was peeled off from the base material at a constant speed of 50 mm / min at a constant temperature of ° C, the force required for the peeling was read, and the average value was expressed in kg / cm.

Slip angle: The obtained non-slip pallet is placed in a constant temperature room at a predetermined temperature, a beer crate containing 26 kg of sand is placed on the non-slip, and one end of the pallet is lifted and inclined. The angle at which the crate began to slip was indicated by the average of three times. It can be seen that a good anti-slip effect is exhibited from a low temperature atmosphere to a high temperature atmosphere.

Example 2 The composition of the anti-slip material used in Example 1 was modified polyolefin (maleic anhydride modified product) with maleic anhydride of 500%.
A non-slip material was welded in the same manner as in Example 1 added so as to become ppm, and the 180 ° peel strength was measured.
/ Cm. The sliding angle is 29 ° (20 ° C),
30 ° (40 ° C) and 26 ° (-10 ° C).

Example 3 The composition of the anti-slip material used in Example 2 was 0.1 parts by weight of a heat stabilizer (fatty acid metal salt), 0.3 parts by weight of a light stabilizer (benzotriazole), and a light stabilizer (Sanol) ) 0.08 parts by weight. A non-slip material was welded in the same manner as in Example 1, and 1
When the 80 ° peel strength was measured, it was 7 kg / cm. The sliding angle is 29 ° (20 ° C), 30 ° (40 ° C).
° C) and 26 ° (-10 ° C). This pallet was immersed in a 10% 50 ° C. surfactant solution for one day for a weather resistance test, and cracking and peeling were observed. When the sliding angle of the pallet after the weather resistance test was examined, no significant change was found.

[0026]

The pallet according to the present invention has an excellent anti-slip effect and its durability, and particularly exhibits a stable anti-slip effect when used at high and low temperatures. It is effective as a pallet for cases where heat treatment is required in a heated state or for carrying work in a refrigerator.

Claims (2)

[Claims] 1. A polyolefin resin pallet in which a non-slip material is provided on a pallet body formed by molding a polyolefin resin by heat welding, wherein the non-slip material is Mw (weight average molecular weight) / Mn (number average molecular weight). A pallet made of a polyolefin resin, comprising a composition containing a polyolefin resin having a degree of dispersion of 4 or less as a main component as a main component. 2. The polyolefin resin pallet according to claim 1, wherein the polyolefin resin having a degree of dispersion of 4 or less is a polyolefin resin obtained by using a metallocene polymerization catalyst.