JPH1029711A - Carrier belt and lap join method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent resistance to heat, water dissolution and contamination, facilitate work and perform strong joining by making a thermoplastic resin composition of polyolefin. SOLUTION: A carrier belt 1 has a four-layer structure including bottom canvas, an intermediate resin layer, intermediate canvas and a cover resin layer. Herein, polyolrefin is used for the cover resin and, for the canvas, the canvas having the warp and the weft made of polyester multi-filaments is used. For the carrier belt 1, a level difference is provided between the intermediate resin layer and the intermediate canvas in both ends so as to superpose both ends of the belt on each other at the time of sticking, and joining sections 2 and 3 are made. An adhesive is applied to the joining sections 2 and 3 and these are laminated and stuck together on base such as a plywood board. Further, a reinforcing tape 4 is placed on the stuck part and stuck by ironing or the like, a joint section is fixed and then joining is easily performed by pressing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transport belt excellent in heat resistance, biosafety, non-contamination, and the like, and a lap joint method for a transport belt that facilitates joint work.

[0002]

2. Description of the Related Art Conveying belts are widely used for conveying raw materials such as foods and luxury goods, intermediate products and products. The conveyor belt generally has a structure in which a thermoplastic resin composition and a canvas are sequentially laminated, and typically includes a front cover (thermoplastic resin composition) / intermediate canvas / cushion (thermoplastic resin composition). ) / Bottom canvas having a four-layer structure.

[0003] Since the transport belt transports raw materials such as foods and luxury goods, intermediate products, products, and the like, biosafety is required. In addition, there is a problem that the belt is corroded or deteriorated in physical properties by a transported object or a cleaning detergent. Furthermore, since foods may be processed during transportation, such as steaming and humidity control, heat resistance, hydrolysis resistance, biosafety, and non-staining properties are required depending on the application. Further, since the transport belt is used by being dynamically wound around two or more rollers or pulleys, it is required to have appropriate flexibility and bending fatigue resistance. In consideration of these necessary characteristics, conventionally, a thermoplastic resin composition layer mainly composed of a polyurethane resin or a polyvinyl chloride resin has been used.

However, in recent years, the issues of environment and refuse have been actively discussed, and as for the transport belt, recycling of used materials, and safety of landfill and incineration when discarded, are considered. It is becoming. With conventional products,
When polyvinyl chloride resin burns, hydrogen chloride gas,
It is known that phosgene and the like are generated, and when the polyurethane resin is burned, nitrogen oxides and cyan gas are generated, and it is said that there is a problem with the conveyance belt using these resins in terms of incineration safety. I can't get it.

[0005] For this reason, there is a demand for the development of a conveyor belt that does not use a polyvinyl chloride resin or a polyurethane resin. Polyolefin-based thermoplastic elastomers and soft polyolefin resins can be considered as alternatives to these resins. However, polyolefin-based thermoplastic elastomers are generally prepared by mixing an ethylene-propylene copolymer and polypropylene and performing dynamic vulcanization, and unreacted products of a crosslinking agent added at this time are used. It may be extracted by n-heptane, and may not pass the food hygiene test according to the Ministry of Health and Welfare Notification No. 20 of 1982. From the viewpoint of biosafety, it is used as a conveyor belt for food or luxury goods. Need attention.

On the other hand, a soft polyolefin resin is softened by adding a large amount of waxes to polyethylene or polypropylene, but the wax tends to be lost from the resin with time, and the physical properties tend to deteriorate. In addition, as a method of softening, there is a method of copolymerizing ethylene or propylene with another α-olefin. In this case, as the copolymerization ratio of the α-olefin increases, the flexibility of the resin increases, but at the same time, the melting point decreases and the heat resistance cannot be obtained. Conventionally, a commercially available soft low-density polyethylene such as a linear low-density polyethylene has not been found to have practically necessary flexibility and heat resistance for a transport belt.

Further, since the transport belt is used by being wound around a roller, it is continuously subjected to a bending stimulus. In order to withstand this, it is necessary that the adhesive strength and heat resistance between the resin layer and the canvas be high, but olefin-based materials are generally difficult to bond, and the adhesive properties of commercially available adhesives are low. This was insufficient, and there was a problem in the heat resistance of adhesive strength.

In order to manufacture a conveyor belt, it is necessary to join both ends of the belt to make it endless. Conventionally, a finger joint method, a lap joint method, and a double finger joint method have been mainly used as a joint method of a conveyor belt. However, these joint methods can be applied to polyurethane belts and polyvinyl chloride belts, which have conventionally been mainstream as resin conveyor belts, but have the following problems when applied to polyolefin belts.

In the finger joint method, as shown in FIG. 2, a notch is formed at both ends of the belt so that both ends are aligned, and a tape made of the same material as the cover resin is placed on the belt and pressed to perform joint. In the case of a polyolefin belt, since the joint strength is weak, there are problems in physical properties such as weakness in repeated bending and easy crack propagation.

The lap joint method is as shown in FIG.
Steps 2 and 3 at both ends of belt
The adhesive is applied to the joining portion 2 and the joining portion 3 and then overlapped. In the case of a polyolefin belt, the adhesive for polyolefin generally has low tackiness and requires heating. However, there is a disadvantage that the joint forming workability is poor and cannot be applied to the joint work on site.

FIG. 4 shows a double finger joint method.
As described above, a finger joint and a lap joint method are combined and can be applied to a polyolefin belt, but there are problems such as difficulty in construction and necessity of pretreatment.

[0012]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a conveyor belt having excellent heat resistance, hydrolysis resistance, biosafety, non-staining, landfill safety and incineration safety, and a work belt. It is an object of the present invention to provide a method of jointing a conveyor belt which can be easily and firmly joined.

[0013]

A first aspect of the present invention is a conveyor belt formed by laminating a canvas and a thermoplastic resin composition, wherein the thermoplastic resin composition is a conveyor belt made of polyolefin. It is. The second invention is a lap joint method for a transport belt in which both ends of a transport belt are overlapped and joined, and an adhesive is applied to a joining portion, and after attaching the joining portion, the joining portion is attached. Is a lap joint method for a transport belt in which a reinforcing tape is stuck on top. Hereinafter, the present invention will be described in detail.

The transport belt of the present invention is obtained by laminating a canvas and a thermoplastic resin composition. In the transport belt of the present invention, the thermoplastic resin composition is made of a polyolefin. Here, “comprising a polyolefin” means that the composition is mainly composed of a polyolefin, and the polyolefin may be used alone or may contain other thermoplastic resin in addition to the polyolefin. Examples of the polyolefin include a polyolefin-based thermoplastic elastomer and a soft polyolefin resin.

The above-mentioned polyolefin has the following structure:
Blend of polypropylene and ethylene-propylene copolymer; mixture of polypropylene and ethylene-propylene copolymer and dynamic vulcanization (so-called polyolefin-based thermoplastic elastomer); polypropylene and ethylene-propylene copolymer Are integrated at the molecular level by a chemical reaction; polyethylene or polypropylene with a large amount of waxes added; ethylene or propylene copolymerized with an α-olefin; and the like.

Of these, and are preferable because of their excellent safety for living bodies. Especially,
And are preferable because the change in physical properties with use is extremely small.

Further, among them, a copolymer of ethylene and an α-olefin, wherein the content of the α-olefin is 8 to 20% by weight and the melting point is 90 to 11
A temperature of 5 ° C. is preferable because it has both heat resistance and flexibility necessary for practical use as a transport belt. The above α-
If the olefin content is less than 8% by weight, flexibility is insufficient, and if it exceeds 20% by weight, the melting point is lowered and the heat resistance becomes poor. More preferably, it is 12 to 20% by weight. Further, if the melting point of the polyolefin is less than 90 ° C., the strength and heat resistance of the resulting transfer belt are poor, which is not suitable for practical use. And poor bending fatigue resistance. The temperature is more preferably 90 to 108 ° C.

The above-mentioned α-olefin has 3 to 12 carbon atoms.
Which is an aliphatic unsaturated hydrocarbon having a double bond at a molecular terminal. When the number of carbon atoms exceeds 12, the copolymerization reactivity decreases, and not only a copolymer having a desired copolymerization ratio cannot be obtained, but also the composition tends to be nonuniform, and in the case of a linear α-olefin, Since crystallization of side chains occurs, the effect of imparting flexibility cannot be obtained. More preferably 4 to 10 carbon atoms
It is. The α-olefin is introduced to reduce the crystallinity of polyethylene in the polyolefin and to provide appropriate flexibility.

Such a polyolefin can be obtained, for example, by synthesizing a linear low-density polyethylene having a desired α-olefin content using a Ziegler-Natta catalyst. However, since the copolymer obtained by this method has a wide range of molecular weight distribution and copolymer composition distribution,
The belt cannot satisfy the required strength, heat resistance, flexibility and bending fatigue resistance. Therefore, it is necessary to purify this to remove low molecular weight components as much as possible. In addition, it can be synthesized by using a metallocene catalyst. Polyolefins synthesized using metallocene catalysts have narrow molecular weight distributions and copolymer composition distributions, so that desired physical properties can be obtained without particular purification.

In the transport belt of the present invention, the polyolefin has a narrow molecular weight distribution and composition distribution, has long chain branches, high strength, good heat sealability, low hexane extraction rate, and excellent workability. Therefore, those synthesized using a metallocene catalyst are preferable. Examples of such a material include affinity and engagement manufactured by Dow Chemical Company.

In the conveyor belt of the present invention, examples of the canvas include polyester yarn, cotton yarn, rayon yarn and the like. Above all, a canvas made of polyester yarn is preferable because it has excellent strength and flexibility and does not generate toxic gases such as nitrogen oxides during combustion. The above-mentioned canvas is not particularly limited with respect to the woven structure, the thickness of the yarn, and the type of yarn such as monofilament, multifilament, and spun yarn.

In the above-mentioned canvas, an oil agent, a surfactant and the like are used at the time of weaving. From the viewpoint of incineration safety, those containing no nitrogen compound or halide are preferable. However, even if they are included, they are very small in quantity and may be acceptable.

From the viewpoint of the adhesion between the canvas and the thermoplastic resin composition, the use of an oil agent or a surfactant containing a nitrogen compound or a halide provides a higher adhesive strength.
This is preferable because the variation in the adhesive strength is small. The reason may be that the interaction between the canvas and the adhesive is enhanced by the presence of a nitrogen-containing functional group or a halogen-containing functional group of an oil agent or the like.

As a method for laminating the above-mentioned canvas and the above-mentioned thermoplastic resin composition, an adhesive made of a polyethylene copolymer is applied to the above-mentioned canvas and dried, and then the above-mentioned thermoplastic resin composition is thin-film-coated on the above-mentioned canvas. The extrusion lamination method of pressing and integrating while melt-extruding into a shape, or the method of continuously heating and pressing the film of the thermoplastic resin composition on the canvas coated with the adhesive is preferable in terms of quality stability and cost. .

In the transport belt of the present invention, the adhesive may be an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-carboxyl group-containing monomer copolymer,
Further, those containing an epoxy resin are preferred because they provide high adhesive strength and are excellent also in terms of safety.

The carboxyl group-containing monomer includes, for example, maleic acid, acrylic acid, methacrylic acid;
These acid anhydrides or derivatives can be mentioned.
When an acid anhydride or a derivative is used as the carboxyl group-containing monomer, it can be converted to an acid form by hydrolysis or the like after copolymerization.

In the transport belt of the present invention, the adhesive is such that the ethylene-vinyl acetate copolymer has a vinyl acetate content of 22 to 38% by weight and the ethylene-vinyl acetate-carboxyl group-containing monomer has a vinyl acetate content of 22 to 38% by weight. A polymer having a vinyl acetate content of 22 to 38% by weight is preferred. If the content is less than 22% by weight, it will not be dissolved in a suitable solvent, so that it will be difficult to bond the canvas, which will increase the cost of the bonding process and destabilize the quality. At the same time as the adhesiveness to the resin composition is reduced, the melting point of the adhesive layer is reduced, so that the heat resistance of the adhesive is inferior.

The above-mentioned adhesive is used in an amount of 10 to 90 parts by weight of the ethylene-vinyl acetate-carboxyl group-containing monomer copolymer per 100 parts by weight of the ethylene-vinyl acetate copolymer.
% By weight is preferred. When the ethylene-vinyl acetate-carboxyl group-containing monomer copolymer has a suitable affinity for the polyolefin and strongly adheres to canvas fibers via the epoxy resin due to the carboxyl group, it is less than 10% by weight. If the adhesiveness is insufficient and exceeds 90% by weight, the above-mentioned ethylene-vinyl acetate-carboxyl group-containing monomer copolymer has low crystallinity itself, and thus lacks mechanical properties such as tensile modulus and yield stress. .
More preferably, it is 25 to 75% by weight.

The above-mentioned adhesive is rich in the mechanical properties such as the tensile modulus and the yield stress of the above-mentioned ethylene-vinyl acetate-carboxyl group-containing monomer copolymer, so that it is rich in these mechanical properties, An ethylene-vinyl acetate copolymer having high compatibility with a vinyl acetate-carboxyl group-containing monomer copolymer is blended. The ratio of the two resins in the adhesive may be appropriately selected according to the thermoplastic resin and the canvas from the viewpoints of flexibility, heat resistance, adhesive strength, and permeability to the canvas.

The carboxyl group content of the above-mentioned ethylene-vinyl acetate-carboxyl group-containing monomer copolymer is 5% by potassium equivalent (mass (mg) of potassium hydroxide required to neutralize 1 g of the copolymer). ~ 25 is preferred. When it is less than 5, adhesion to the canvas fiber via the epoxy resin becomes insufficient, and when it exceeds 25, the affinity with the polyolefin and the ethylene-vinyl acetate copolymer decreases, and Adhesive strength is reduced. More preferably, it is 7 to 15.

The epoxy resin is not particularly limited as long as it is a compound having two or more epoxy groups in the molecule. The amount of the epoxy resin to be added varies depending on the epoxy equivalent, the molecular weight, and the adhesive strength, flexibility, bending fatigue resistance, and the like desired as a conveyor belt, but the ethylene-vinyl acetate copolymer and the ethylene-vinyl acetate 20 per 100 g of the mixture with the carboxyl group-containing monomer copolymer
~ 80 g is preferred. If it is less than 20 g, the adhesive strength between the adhesive layer and the canvas fiber becomes insufficient, and if it exceeds 80 g, the adhesive layer tends to be hard and brittle, and the bending property and the bending fatigue resistance as a conveyor belt are reduced. Lower. More preferably, the weight is 25 to 45 g.

The above adhesive can be used by dissolving it in an organic solvent. Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene and benzene. These can be used alone or in combination. The above-mentioned solvent is the above-mentioned aromatic hydrocarbon-based solvent, an ester such as ethyl acetate; an aliphatic hydrocarbon such as hexane; a ketone such as methyl ethyl ketone; a halogen-containing solvent such as methylene chloride; an alcohol; , Amides, sulfoxides and other solvents may be used as a mixture.

The adhesive solution preferably has a concentration of 10 to 30% by weight. If the amount is less than 10% by weight, the adhesive permeates into the canvas fibers and does not remain on the surface of the canvas. Therefore, no adhesive force is exhibited, and if it exceeds 30% by weight, coating becomes difficult. More preferably, it is 12 to 20% by weight.

The above-mentioned adhesive is used in order to further increase the adhesive strength, heat resistance and water resistance within the range where there is no problem in terms of incineration safety. It is preferable to contain a polyisocyanate compound in addition to the carboxyl group-containing monomer copolymer and the epoxy resin. The polyisocyanate compound has two isocyanate groups in the molecule.
There is no particular limitation as long as the compound has the above.

The amount of the polyisocyanate compound varies depending on the isocyanate equivalent, the molecular weight, the desired adhesive strength and the like, but the amount of the ethylene-vinyl acetate copolymer and the ethylene-vinyl acetate-carboxyl group-containing monomer copolymer is different. 20 to 80 g is preferable for 100 g of the mixture. If the content is less than 20% by weight, the desired effect of improving the adhesive performance cannot be obtained. If the content is more than 80% by weight, the adhesive layer tends to be hard and brittle, and has flexibility and bending fatigue resistance as a conveyor belt. Lower. More preferably, it is 25 to 45 g. The transport belt of the present invention can be suitably used as a light-load transport belt.

Hereinafter, the second present invention will be described in detail. In the lap joint method for a transport belt according to the present invention, both ends of the transport belt are overlapped and joined. In the lap joint method for a transport belt according to the present invention, an adhesive is applied to the joining portion, the joining portion is attached, and a reinforcing tape is attached on the joining portion.

The reinforcing tape is preferably made of the same material as the conveyor belt because it can reinforce the lack of volume at the joint portion and prevent the strength of the joint portion from decreasing. The reinforcing tape is preferably attached using a small heater such as a hand welder or an iron.

In the lap joint method for a conveyor belt according to the present invention, the reinforcing tape is heat-sealed with a small heater such as an iron to fill gaps in the joining portion and give strength to the joint portion. Also, the joint part can be fixed, and the joint work can be facilitated. Further, since a small heating machine is used, the construction is simple.

In the lap joint method for a transport belt according to the present invention, it is preferable that the reinforcing tape is attached to the outer peripheral side when an endless transport belt is formed by joining both ends of the transport belt. .

In the lap joint method for a transport belt of the present invention, since the reinforcing tape is attached with an iron or the like, it can be preferably used as a lap joint method for a polyolefin belt having a low melting point and a high releasability. In particular, it is preferable to use the conveying belt of the present invention as a method for joining. The adhesive is not particularly limited as long as it can bond the transport belt.

In the lap joint method for a transport belt of the present invention, it is preferable that the joining portion of the transport belt has a step at both ends so that both ends of the belt overlap when bonded. . Further, the angle of the notch in the step of the joining portion is preferably 60 °.

The size of the reinforcing tape is not particularly limited, but is preferably a size that reinforces the gap of the joining portion and does not become too thick. In the above-described lap joint method of the transport belt, it is preferable that the reinforcing tape is attached and then fixed by a press or the like.
In the lap joint method for the transport belt, the joint can be firmly joined by attaching the joining portion with an adhesive and then attaching the reinforcing tape to the gap between the joining portions after the joining.

In the above-described lap joint method of the transport belt, immediately after the adhesive is applied to the joining portion,
The reinforcing tape may be attached from the joining portion to the upper surface of the transport belt using a small heater such as an iron, and then the joining portion may be attached. Thereby, the gap can be filled in the joint portion, and the joint portion can be more closely contacted to increase the strength. In this case, it is preferable that, when the joining portions are attached, the reinforcing tape is press-bonded to fill the gap between the joining portions.

[0044]

Embodiments of the present invention will be described below. The lap joint method of the transport belt of the present invention,
It can be implemented as shown in FIG. In FIG. 1, the conveyor belt 1 has a four-layer structure of a bottom canvas / intermediate resin layer / intermediate canvas / cover resin layer. In the transport belt 1, a joining portion 2 and a joining portion 3 are formed by providing a step between the intermediate resin layer and the intermediate canvas at both ends so that both ends of the belt overlap when the belt is attached. An appropriate angle of the cut of the step of the joining portion 2 and the joining portion 3 is 60 °. An adhesive is applied to the joining portions 2 and 3, and the joining portions 2 and 3 are overlapped and bonded on a table such as a plywood plate. Further, the reinforcing tape 4 is placed on the bonded portion and bonded with an iron or the like. As a result, the joint portion is fixed, and thereafter, the joint can be easily formed by pressing or the like.

[0045]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 and 2 and Comparative Examples 1 to 3 Affinity PF1140 manufactured by Dow Chemical Co., Ltd. was used as a cover resin, and canvas consisting of polyester multifilaments in both warp and weft was used as canvas. The adhesive having the composition shown in Table 1 was used.

The canvas was dipped with the uniformly dissolved adhesive composition, and subsequently heated and dried at 120 ° C. for 5 minutes to perform the bonding treatment. By laminating the molten resin on the canvas, a conveyor belt material having a four-layer structure of a bottom canvas / intermediate resin layer / intermediate canvas / cover resin layer was obtained. The thickness of the resin layer was about 0.8 mm for both the middle and the cover.

The adhesion test was performed by cutting out a test piece having a width of 25 mm and a length of 15 cm from this material and measuring the T peeling force at the interface between the intermediate resin layer and the intermediate canvas at a peeling speed of 50 mm / min. In the actual belt running test, a belt having a circumference of 1 m was obtained by joining the front and back of a 50 cm wide belt material, and this was wound around two 80 mm diameter pulleys, and a tension of 250 N was applied to the belt. Meanwhile, the belt was run at 100 m / min.
Those that withstood running for 8 hours × 30 days per day passed (o), and those that became unable to run due to adhesion failure between the resin layer and the canvas on the way were failed (x). The results are shown in Table 1.

[0049]

[Table 1]

In Table 1, 1) is an ethylene-vinyl acetate copolymer manufactured by Du Pont-Mitsui Polychemicals, and 2) is ethylene-vinyl acetate manufactured by DuPont Mitsui Polychemicals.
Carboxyl group-containing monomer copolymer, 3) represents polyglycerol polyglycidyl ether manufactured by Nagase Kasei Kogyo Co., Ltd., and 4) represents polyisocyanate compound manufactured by Kasei Upjohn Co., Ltd.

[0051]

Since the transport belt of the present invention is constructed as described above, it is excellent in heat resistance, hydrolysis resistance, biological safety, non-staining property, landfill safety and incineration safety. Further, in the lap joint method for a transport belt according to the present invention, since a reinforcing tape is stuck on the joining portion, the work is easy and the joint can be firmly performed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a lap joint method for a transport belt of the present invention.

FIG. 2 is a schematic view showing a conventional finger joint method.

FIG. 3 is a schematic view showing a conventional lap joint method.

FIG. 4 is a schematic view showing a conventional double finger joint method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conveyor belt 2 Joining part 3 Joining part 4 Reinforcement tape

Claims (9)

[Claims] 1. A conveyor belt comprising a canvas and a thermoplastic resin composition laminated, wherein the thermoplastic resin composition is made of a polyolefin. 2. The polyolefin is a copolymer of ethylene and an α-olefin, wherein the content of the α-olefin is 8 to 20% by weight and the melting point is 90 to 11%.
The transport belt according to claim 1, wherein the temperature is 5 ° C. 3. The transport belt according to claim 1, wherein the polyolefin is synthesized using a metallocene catalyst. 4. A method in which an adhesive made of a polyethylene copolymer is applied to a canvas, dried, and then the thermoplastic resin composition is melt-extruded into a thin film on the canvas and pressed and integrated to obtain the fabric. 4. The conveying belt according to 2, 3 or 4. 5. The transport belt according to claim 4, wherein the adhesive contains an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-carboxyl group-containing monomer copolymer, and an epoxy resin. 6. The adhesive according to claim 1, wherein the ethylene-vinyl acetate copolymer has a vinyl acetate content of 22 to 38% by weight, and the ethylene-vinyl acetate-carboxyl group-containing monomer copolymer has a vinyl acetate content of 22 to 38% by weight. The transporting belt according to claim 5, wherein the content of the transporting belt is about 38% by weight. 7. The transport belt according to claim 5, wherein the adhesive contains a polyisocyanate compound. 8. A lap joint method for a transport belt in which both ends of a transport belt are overlapped and jointed, wherein an adhesive is applied to a joining portion, and the joining portion is attached to each other. Lap joint method for a conveyor belt, characterized in that a reinforcing tape is attached to the belt. 9. A method of lap jointing a transport belt according to claim 1, wherein both ends of the transport belt are overlapped and jointed, wherein an adhesive is applied to the joining portion. After applying and bonding the mating part,
A lap joint method for a transport belt, wherein a reinforcing tape is attached to the joining portion.