JP2847300B2 - Sheet pallet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sheet pallet, particularly to a cold-resistant or highly rigid sheet pallet.

More specifically, a sheet composed of a three-component composition of a propylene polymer, a polyethylene resin such as high-density polyethylene and a rubber-like substance, and a soft rubber or resin such as ultra-low-density polyethylene, which has cold resistance, rigidity The present invention relates to a sheet pallet having excellent mechanical strength, such as excellent operability, in which the friction coefficient of the loading surface of the sheet is larger than the friction coefficient of the back surface.

[Conventional technology]

With the recent resource saving, a system using a light sheet pallet instead of a conventional wooden pallet or a plastic valet is rapidly spreading in the field of cargo distribution.

 Sheet pallets (a) save space for storage (b) are inexpensive (c) can be omitted in some cases (d) can be easily manufactured (e) can improve work efficiency It has many advantages.

Various types of sheet pallets manufactured using plastic as a main raw material and having characteristics in the structure, shape and composition have been proposed.

For example, a `` table for carrying '' disclosed in Japanese Utility Model Publication No. 55-16821 is used to transport and transfer packaged cargo, at least on the upper surface of a sheet pallet having a thickness of 0.5 to 3.2 mm of polyolefin resin. The rough surface is formed, and the upper surface is formed to be rougher than the lower surface, so that the coefficient of static friction between the upper surface and the cargo is higher than the coefficient of sliding friction between the lower surface and the platen. As a characteristic, the cargo handling work is smoothed.

In addition, the "slipper pallet" disclosed in Japanese Patent Publication No. 58-1023 has a polyolefin resin as a main component, an apparent specific gravity is engraved with a ruled line on a foamed sheet of 0.4 to 0.7, and tabs are provided at one or more places around the periphery. There has been proposed a sheet pallet characterized by being provided with the object of preventing breakage of a ruled line portion and improving impact resistance and the like.

By these methods, basic properties such as water resistance, oil resistance, chemical resistance, strength, heat resistance, impact resistance, etc. of the sheet pallet can be satisfied, but the cold resistance is still insufficient. I can't say.

Further, as a material for improving cold resistance and impact resistance, a propylene block copolymer or a brand composition of polypropylene and an ethylene / propylene copolymer rubber has been developed.

For example, the applicant has disclosed a `` cold-resistant sheet pallet '' disclosed in Japanese Patent Application Laid-Open No. Sho 62-174233, which uses a composition comprising a propylene polymer and a specific ethylene / α-olefin copolymer to exhibit cold resistance. Suggests improvements.

Further, a composition containing ethylene / propylene copolymer rubber or / and polyethylene for the purpose of improving the impact resistance of polypropylene (for example, JP-B-39-18746)
No., JP-B-41-7345, JP-A-55-104334, etc.)
Is also known.

However, in recent years, logistics has become more complicated, and as the range of use has expanded, characteristics of both high and low temperatures have been demanded.
In consideration of use at ultra-low temperatures such as in a freezer, it is becoming extremely important to improve strength, heat resistance, and the like, as well as low-temperature impact resistance.

In general, in plastic materials, physical properties such as strength, rigidity, heat resistance and the like are incompatible with low-temperature impact resistance. Therefore, there is a strong demand for the development of a sheet pallet in consideration of a balance of these various questions.

[Problems to be solved by the invention]

In view of the above, the present invention provides a sheet pallet with improved workability, particularly in terms of balance of rigidity and low-temperature impact resistance, by examining the material composition to improve the brittleness temperature. It is the purpose.

Another object of the present invention is to select a particularly low-density polyethylene in the composition, thereby obtaining a composition in which the mutual dispersibility of polypropylene and polyethylene is good (good dispersion). The present invention provides a sheet pallet excellent in mechanical strength such as rigidity, heat resistance, and the like because impact resistance does not decrease even when a relatively large amount of filler is filled.

[Means for solving the problem]

The present inventor has conducted intensive studies along the above-mentioned object, and as a result, by mixing an ethylene (co) polymer such as a propylene-based polymer and a high-density polyethylene and an ultra-low-density polyethylene at a specific ratio, the cold resistance or the cold resistance is remarkably increased. The present inventors have found that a sheet pallet having excellent rigidity can be obtained, and have completed the present invention.

That is, the present invention relates to (A) a propylene-based polymer: 55 to 90% by weight (B) ethylene having a density of 0.91 or more to 0.97 g / cm ³ or a polymer of ethylene and an α-olefin; At least one ethylene (co) polymer selected from a polymer, a copolymer of ethylene-unsaturated carboxylic acid or a derivative thereof ... 5 to 30% by weight (C) ethylene and α having 3 to 12 carbon atoms - maximum peak temperature 1 by ultra low density polyethylene ...... 5-30% by weight having the following properties obtained by polymerizing an olefin density 0.86~0.91g / cm less than ³ differential scanning calorimetry (DSC)
Polyolefin-based resin composition containing at least 00 ° C and a boiling n-hexane insoluble content of 10% by weight or more (however, A + B + C
Is 100% by weight), the friction coefficient of the loading surface is larger than the friction coefficient of the back surface, and the thickness is 0.3 to 1
A sheet pallet that is 0mm.

The propylene-based aggregate of the component (A) of the present invention includes a propylene homopolymer and other α-
Examples thereof include copolymers with olefins and mixtures thereof.

More specifically, isotactic polypropylene,
Syndiotactic polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, propylene-1-butene copolymer and the like can be used.

The propylene content of the copolymer is preferably at least 60% by weight or more.

Further, a melt float of the propylene polymer (hereinafter referred to as a melt float)
MFR) is 0.1 to 10 g / 10 minutes, preferably 0.5 to 5 g /
A range of 10 minutes is desirable for maintaining rigidity and heat resistance.

When the MFR is less than 0.1 g / 10 minutes, the flowability of the molten resin is deteriorated, so that it is difficult to obtain a good sheet, and there is a possibility that the productivity may be reduced.

If the MFR exceeds 10 g / 10 minutes, there is a concern that the strength and other physical properties of the sheet may be reduced.

Component (B) of the present invention, a density of 0.91 or more to 0.97 g / cm ³ of ethylene or a polymer of ethylene and an α-olefin,
At least one ethene (co) polymer selected from an ethylene-vinyl ester copolymer and a copolymer with an ethylene-unsaturated carboxylic acid or a derivative thereof includes: (B1) a Ziegler catalyst or a high-pressure radical polymerization. ethylene homopolymer or an ethylene and α- olefin copolymers such as the density of 0.94 / cm ³ or more ethylene homopolymer or ethylene and α- olefin copolymer, medium and high density polyethylene, or ethylene and propylene , Butene-1, 4-methylpentene-1,
Copolymers with α-olefin such as hexene-1 and the like.

Examples of the (B2) low-density polyethylene having a density of 0.94 / cm ³ or less include linear low-density polyethylene (LLDPE), high-pressure low-density polyethylene (HpLDP), and a mixture thereof. (B3) Ethylene-vinyl ester copolymer is a vinyl ester monomer mainly composed of ethylene such as vinyl propionate, vinyl acetate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate, and vinyl trifluoroacetate. It is a copolymer of a monomer.
Among them, particularly preferred is vinyl acetate.

(B4) Ethylene-unsaturated carboxylic acid or a copolymer thereof with a derivative thereof is unsaturated such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, etc., having ethylene as a main component. Carboxylic acids: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate,
Propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, Monomethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, and copolymers with unsaturated carboxylic acid alkyl ester monomers such as ethyl acrylate are particularly preferred. Can be

Specific examples of the above ethylene copolymer include ethylene /
Acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid / ethyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene /
Examples include random copolymers such as vinyl acetate copolymers and ethylene / vinyl acetate / ethyl acrylate copolymers.

The melt flow rate of the ethylene (co) polymer is:
The range of 0.05 to 50 g / 10 min, preferably 0.1 to 10 g / 10 min is desirable for improving the compatibility with the polypropylene polymer.

The rubbery substance (C1) of the component (C) of the present invention includes ethylene-propylene random copolymer rubber, ethylene-propylene-diene random copolymer rubber, natural rubber, isobutene rubber, butadiene rubber, 2-polybutadiene, styrene-butadiene random copolymer rubber, chloroprene rubber, nitrile rubber, styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, etc. It may be a mixture.

Among them, ethylene / propylene / diene random copolymer rubber and ethylene / propylene random copolymer rubber are particularly preferable.

These two rubbers are superior in thermoplasticity to other rubbery substances, are easily dispersed by melt-kneading, and do not have a unique odor compared to SBR, isoprene rubber, nitrile rubber or butadiene rubber, Alternatively, since it can be obtained in the form of pellets, it has advantages in operation, such as easy measurement and handling at the time of compounding, and a high degree of freedom in selecting the type of the composition producing apparatus.

As the diene component of the ethylene-propylene-diene random copolymer rubber, any of ethylidene norbornene, dicyclopentadiene, 1,4-cyclohexadiene and the like can be used.

The Mooney viscosity of these rubbery substances is (ML _{1 + 4} 100
C) in the range of 10 to 100, preferably (ML _{1 + 4} 10
0 ° C) 20-90. (ML _{1 + 4} 100 ° C) If less than 10 is used, the effect of improving the impact resistance is hardly obtained.
(ML _{1 + 4} 100 ° C) If it is more than 100, the dispersion in the matrix resin is poor.

(C2) Ultra low density polyethylene (ULDPE)
It refers to polyethylene having a property of 0.86 to less than 0.910 g / cm ³ and showing intermediate properties between linear low-density polyethylene and ethylene / α-olefin copolymer rubber.

For example, specific ethylene-α- having a density of less than 0.860 to 0.910 g / cm ³ , a maximum peak temperature (Tm) of 100 ° C. or more by differential scanning calorimetry (DSC), and a boiling n-hexane insoluble content of 10% by weight. An olefin copolymer, which is polymerized using a catalyst comprising a solid catalyst component containing at least titanium and / or vanadium and an organoaluminum compound.

The above ULDPE is a resin having both a high crystalline portion represented by a linear low-density polyethylene and an amorphous portion represented by an ethylene / α-olefin copolymer rubber, and has the mechanical strength and heat resistance characteristic of the former. With the latter, rubber-like elasticity and low-temperature impact resistance, which are the characteristics of the latter, coexist in a good balance,
When used in the present invention, as described below, a thermoplastic resin composition having excellent performance over a wide range is obtained, which is extremely useful.

The above-mentioned melt flow rate is used in the range of 0.01 to 50 g / 10 minutes, preferably 0.05 to 10 g / 10 minutes.

The compounding ratio of the composition of the present invention is 55 to 90% by weight of the polypropylene polymer (A), 5 to 30% by weight of the ethylene (co) polymer of the component (B), and the rubbery substance of the component (C). Or 5 to 30% by weight of ultra low density polyethylene (however, A + B
+ C is 100% by weight).

When the amount of the component (B) in the composition is less than 5% by weight,
No improvement in impact resistance, especially low-temperature impact resistance, is achieved.

When the amount exceeds 30% by weight, strength, rigidity and heat resistance are poor.

Similarly, if the amount of the component (C) in the composition is less than 5% by weight, the low-temperature impact resistance is not improved, and if it exceeds 30% by weight, the strength, rigidity and heat resistance are poor. Becomes

As the compounding method of the above composition, conventionally known ones such as an open-type mixing roll, a non-open-type Banbury mixer, an extruder, a kneader, a twin-screw extruder, a tumbler, and a Henschel mixer can be used.

As a kneading method, dry blending, melt mixing, or mixing these three components while polymerizing may be used.

According to the present invention, after mixing (A), (B) and (C) at a desired ratio, a sheet is formed by an ordinary method such as extrusion molding (for example, T-die method) or calendering method. Either embossing, sand blasting, corona discharge treatment, flame treatment, plasma treatment, or other surface treatment is applied to the entire or desired portion of the loading surface to roughen the surface, or an ethylene-vinyl acetate copolymer is synthesized on the sheet loading surface. By laminating and laminating anti-slip materials such as rubber, the coefficient of friction of the loading surface is increased to prevent load slip and collapse.

The above-mentioned coefficient of friction varies depending on the packaging material of the cargo such as paper or plastic, and also depends on the shape of the bottom of the cargo, the weight of the cargo, and the like. 0.8, preferably
A range of 0.3 to 0.7 is appropriate.

Furthermore, the thickness of the sheet pallet of the present invention is 0.3 to 10 m
m, preferably in the range of 0.5 to 5 mm.

When the thickness of the sheet pallet is less than 0.3 mm, the mechanical strength such as sheet rigidity is inferior. When the thickness exceeds 10 mm, the characteristics required in the present invention are satisfied, but the weight is large. There is a concern that it will hinder automation and handling of cargo handling.

The target values of the properties of the cold-resistant sheet pallet are a stiffness of 5,000 kgf / cm ² or more and an embrittlement temperature of -50 ° C. or less.

In the present invention, in order to improve heat resistance and rigidity in addition to cold resistance, it is preferable to add an inorganic filler to the above composition.

(A) Propylene-based polymer 55-90% by weight (B) Ethylene having a density of 0.91 or more to 0.97 g / cm ³ or a polymer of ethylene and α-olefin, ethylene-vinyl ester copolymer, ethylene -At least one ethylene (co) polymer selected from copolymers with unsaturated carboxylic acids or derivatives thereof: 5 to 30% by weight (C) ethylene and an α-olefin having 3 to 12 carbon atoms Ultra low density polyethylene having the following properties obtained by polymerization: 5 to 30% by weight Density 0.86 to less than 0.91 g / cm ³ Maximum peak temperature 1 by differential scanning calorimetry (DSC) 1
Polyolefin-based resin composition containing at least 00 ° C and a boiling n-hexane insoluble content of 10% by weight or more (however, A + B + C
The above object can be achieved by using a sheet pallet comprising: (D) an inorganic filler: 5 to 100 parts by weight with respect to 100 parts by weight.

If the amount of the inorganic filler is less than 5 parts by weight, rigidity,
Heat resistance and the like are not sufficiently improved.

If the amount exceeds 100 parts by weight, the low-temperature impact resistance is reduced.

As the inorganic filler (D) of the present invention, various common fillers such as talc, calcium carbonate, carbon black, mica, glass fiber, carbon fiber, aramid resin, asbestos and the like, and those obtained by subjecting these fillers to surface treatment are appropriately used. Can be blended.

Stabilizers, antioxidants as needed in the composition of the present invention,
An ultraviolet absorber, a lubricant, a foaming agent, an antistatic agent, a flame retardant, a crosslinking agent, a plasticizer, a dye, a pigment, and the like can be appropriately compounded.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

[Used resin, etc.] (A) component; (A) polypropylene block copolymer (referred to as PP); [about 10% by weight of ethylene, MFR = 1.5 g / 10 min.] (B) component; (B1) high-density polyethylene (Referred to as HDPE) [Density 0.956 g / cm ³ , MFR = 1.6 g / 10 min Product name: Nisseki Staphrene E715, Nippon Petrochemical Co., Ltd.] (B2) Linear low-density polyethylene (referred to as LLDPE) [Density 0.921 g / cm ³ , MFR = 1.0 g / 10 min Trade name: Nisseki Linirex AF2380, Nippon Petrochemical Co., Ltd.] (B3) Ethylene-vinyl acetate copolymer (referred to as EVA) [density 0.932 g / cm ³ , MFR = 1.0g / 10min Product name: Nisseki Lexlon V260, Nippon Petrochemical Co., Ltd.] (B4) Ethylene-ethyl acrylate copolymer (EEA) [EA content 10wt%, MFR = 1.5g / 10min Product Name: Nisseki Lexlon A2100, Nippon Petrochemical Co., Ltd.) (C) component; rubber-like substance (C1) ethylene-propylene. Random copolymer rubber (referred to as EPR) An ethylene / propylene copolymer rubber was obtained using a vanadium trichloride / ethyl aluminum sesquichloride catalyst. The obtained copolymer rubber had a propylene content of 19 mol%, a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 73, and a density of 0.862 g / cm ^3.
Met.

No peak due to DSC was observed, and therefore, the Tm
Was not present, and no C ₆ insolubles were found.

(C2) Ethylene-butene-1 copolymer Using a catalyst comprising triethylaluminum and a solid catalyst component obtained from substantially anhydrous magnesium chloride, 1,2-dichloroethane and titanium tetrachloride, ethylene and butene-1 And ethylene-butene-1
Ultra low density polyethylene (ULDPE) made of copolymer
(1)) was obtained.

This ultra-low density polyethylene (ULDPE (1)) has a butene-1 content of 10 mol%, a density of 0.900 g / cm ³ , a Tm of 120 ° C. and a C ₆
The insoluble content was 82% by weight, and the MFR was 1.5 g / 10 min.

(C3) Ethylene-propylene copolymer Ethylene and propylene are copolymerized using a catalyst comprising triethylaluminum and a solid catalyst component obtained from substantially anhydrous magnesium chloride, anthracene and titanium tetrachloride. An ultra low density polyethylene (ULDPE (2)) comprising an ethylene / propylene copolymer was obtained.

The ethylene / propylene copolymer had a propylene content of 12 mol%, a density of 0.900 g / cm ³ , a Tm of 119 ° C., and a C ₆ insoluble content of 8
2% by weight, MFR = 1.3 g / 10 min.

(C4) Ethylene / butene-1 copolymer Using a vanadyl trichloride / ethylaluminum sesquichloride-based catalyst, an ultra-low density polyethylene (ULDPE (3)) composed of an ethylene / butene-1 copolymer was obtained.

The obtained copolymer had a butene-1 content of 6 mol% and a density of
0.895 g / cm ³ , Tm = 81 ° C., C ₆ insoluble content = 1.5% by weight, MFR = 3.
It was 5 g / 10 min.

[Test and measurement methods]

 (MFR) Conforms to JIS K6760.

(Tensile yield strength) and (Tensile elongation at break) Based on JIS K6760.

(Differential scanning calorimetry (DSC) maximum peak temperature (T
Measurement method of m)) It was measured as the melting point of ultra-low density polyethylene. Approximately 5 mg of a sample was weighed accurately from a hot-pressed film of 100 μm thickness, set in a DSC device, heated to 170 ° C. and maintained at the same temperature for 15 minutes, and then cooled at a rate of 2.5 ° C./min. Cool to ° C. Next, from this state, the temperature is raised to 170 ° C. at a rate of 10 ° C./min, and the temperature at the apex position of the largest peak among the peaks that appeared during the temperature rise from 0 ° C. to 170 ° C. is defined as Tm. .

(Measurement Method of Boiling n-Hexane Insolubles) A 200-μm-thick sheet was formed by using a hot press, and three 20 mm × 30 mm sheets were cut out of the sheet, and the boiling n-sheet was extracted using a double tube Soxhlet extractor. Extract with hexane for 5 hours. Remove the n-hexane insolubles,
After vacuum drying (7 hr, 50 ° C.), the boiling n-hexane insoluble matter is calculated by the following formula: Examples 1 to 3 and Comparative Examples 1 to 13 Each of the above components was subjected to resin temperature 2 using an extruder (120 mmΦ).
Extruding a 1.8 mm thick x 1,600 mm wide sheet under sheet forming conditions of 35 ° C, cooling roll temperature of 100 ° C, and a take-up speed of 2 m / min, and embossing the sheet loading surface (upper surface) to form a sheet pallet The material was manufactured. Table 1 shows the composition and properties of the various sheet pallet materials described above.

 The method of measuring the property value is as follows.

Flexural stiffness; JIS K7106 embrittlement temperature; JIS K6760 [Evaluation results] As is clear from Table 1, in all of the examples of the present invention, the flexural rigidity is high, and the embrittlement temperature is sufficiently low.
Excellent balance between rigidity and low temperature impact resistance.

On the other hand, in the comparative example, these balances were not sufficient, and both could not be satisfied at the same time.

[Effect of the Invention] As described above, the sheet pallet of the present invention is made of a three-component composition of a polypropylene polymer, an ethylene (co) polymer, and an ultra-low density polyethylene,
Not only has good chemical properties such as water resistance, oil resistance, chemical resistance, etc. and can withstand repeated use, but also the balance of strength, rigidity, heat resistance and low temperature impact resistance is much better than conventional ones, In particular, since the improvement of the brittle temperature has been achieved, it can be used without difficulty for a long time in an ultra-low temperature environment.

Claims (2)

(57) [Claims] (A) Propylene polymer: 55 to 90% by weight (B) Ethylene having a density of 0.91 or more to 0.97 g / cm ³ or a polymer of ethylene and α-olefin, ethylene-vinyl ester copolymer At least one ethylene (co) polymer selected from copolymers of ethylene-unsaturated carboxylic acids or derivatives thereof .... 5 to 30% by weight (C) ethylene and α-C 3 to C 12 Ultra-low density polyethylene having the following properties obtained by polymerization with olefin: 5 to 30% by weight Density 0.86 to less than 0.91 g / cm ³ Maximum peak temperature 100 by differential scanning calorimetry (DSC)
° C or higher Polyolefin-based resin composition containing 10% by weight or more of insoluble matter in boiling n-hexane (however, A + B + C
Is 100% by weight), the friction coefficient of the loading surface is larger than the friction coefficient of the back surface, and the thickness is 0.3 to 1
A sheet pallet that is 0mm. 2. The polyolefin resin composition (provided that:
The sheet pallet according to claim 1, wherein (D) an inorganic filler is included in an amount of 5 to 100 parts by weight with respect to 100 parts by weight (the total amount of A + B + C is 100% by weight).