JPH0132062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a buffer sheet.

A foamed resin sheet is used as the buffer sheet. The foamed resin sheet appears to be easy to manufacture because it is sufficient to extrude a resin containing a foaming agent into a sheet and foam it. However, it is not always easy to produce a uniformly foamed sheet over a wide width.
This is because the normal manufacturing process is to first form a sheet and then foam it.
This is because when a sheet-like material is foamed, the sheet is deformed and distorted, making it difficult to obtain a flat sheet without chicks over a wide area, and also tends to cause non-uniform foaming. Therefore, it was necessary to further improve the manufacturing method.

On the other hand, cushioning materials similar to foamed resin sheets include
There is a cellular polyethylene sheet. A cellular polyethylene sheet is made by laminating two non-foamed polyethylene sheets, one of which has disc-shaped ridges formed closely together, and a disc-shaped opening in the raised sheet is closed. This sheet is made by laminating other sheets together and forming a large number of sealed disc-shaped air bubbles in close contact between the two sheets. Cellular sheets can be easily obtained with uniform quality, but they have the disadvantage that the bubbles are easily crushed, and when one bubble is crushed, the cushioning effect is completely lost over a wide area.

Therefore, the inventor attempted to develop a buffer sheet that does not have the above-mentioned drawbacks. As a result, it was discovered that a sheet obtained by adhering or fusing foamed resin particles to a non-foamed resin film or sheet is flexible, has rich cushioning properties, and is suitable as a cushioning sheet. In particular, a mutually impregnated polymer obtained by polymerizing an ethylene polymer impregnated with a styrene monomer is used as foamable particles, which are once foamed to make foamed particles. Alternatively, the above-mentioned buffer sheet can be easily obtained by forming a styrene-based resin into a film or sheet by extrusion molding, and then scattering and fusing the expanded particles onto the film or sheet while the film or sheet is softened. I discovered that. This invention was made based on such knowledge.

This invention involves polymerizing or copolymerizing a certain monomer to contain another monomer, and then polymerizing the monomers in this state to obtain a mutually impregnated polymer. , using an ordinary polymer obtained by polymerizing or copolymerizing monomers constituting the mutually impregnated polymer,
A blowing agent is impregnated into a mutually impregnated polymer, the foamed particles are foamed, the above-mentioned ordinary polymer is formed into a non-foamed film or sheet, and the film or sheet is placed on top of it in a softened state. The present invention relates to a method for manufacturing a buffer sheet, which comprises dispersing the foamed particles or expandable particles and fusing the particles to a film or sheet.

FIG. 1 schematically shows one embodiment of the method of this invention. In FIG. 1, 1 is an expandable particle made of a mutually impregnated polymer, and 2 is an already foamed expanded particle, which is obtained by heating and foaming the expandable particle 1. 3 and 4 are extruders, 5 and 6 are non-foamed films or sheets made of ordinary polymers, and 7 is a fusion sheet in which foamed particles 2 are fused onto the film or sheet 5. , 8 is a cooling tank, 9 is a take-up machine, and 10 is a laminate in which a film or sheet 6 is laminated on a fusing sheet 7. The fusing sheet 7 or the laminate 10 is the buffer sheet that is the object of the method of this invention.

In FIG. 1, the method of the invention is carried out in the following sequence. First, an interimpregnated polymer 1 is made from at least two monomers. In this process, a polymer obtained by polymerizing a certain monomer, such as polyethylene, contains another monomer, such as styrene, and then polymerizes styrene. More specifically, polyethylene is granulated and dispersed in water to form a dispersion, and styrene in which a polymerization initiator, such as benzoyl peroxide or dicumyl peroxide, has been dissolved in advance is added to the dispersion, so that the styrene is included in the polyethylene. state, and in this state, styrene is polymerized. An interimpregnated polymer is thus obtained. This inter-impregnated polymer is then impregnated with a blowing agent to form expandable particles.

The above-mentioned interimpregnated polymer is a kind of graft polymer. That is, the mutually impregnated polymer is said to be produced by polymerizing the styrene contained in polyethylene one after another using polyethylene molecules as a backbone, and by crosslinking the polyethylene molecules. Therefore, unlike a polymer obtained by simply mixing a styrene polymer and an ethylene polymer, the mutually impregnated polymer contains components that are not soluble in organic solvents because it contains crosslinks.
It also has high heat resistance and is difficult to dissolve. For example, interimpregnated polymers obtained by polymerizing styrene in polyethylene contain components that do not dissolve in hot toluene. The proportion of this undissolved portion is called the gel concentration.

As the blowing agent for foaming the interimpregnated polymer, various known blowing agents can be used. For example, it is possible to use an aliphatic hydrocarbon or halogenated aliphatic hydrocarbon having a boiling point lower than the softening point of the interimpregnated polymer, a solid compound that decomposes to generate gas at a temperature below the softening point of the interimpregnated polymer, etc. can. Examples of aliphatic hydrocarbons suitable as blowing agents are propane, butane, pentane, etc., and examples of halogenated aliphatic hydrocarbons are methyl chloride, ethyl chloride, etc. Also, examples of solid compounds that generate gas are soda bicarbonate,
These include azodicarbonamide and dinitrosopentamethylenetetramine.

In the method of the invention, expandable particles of interimpregnated polymers are expanded. To foam, the expandable particles may be heated to a temperature above the softening point of the polymer. In this respect, they are the same as expandable particles made of ordinary thermoplastic resin. For example, by blowing heated steam onto expandable particles made of inter-impregnated polymers, the expandable particles can be easily foamed. thus,
Obtain expanded particles. Since each of the expandable particles is in a separate state, a large amount of particles can be easily and uniformly foamed at once by blowing water vapor into the particles.

The inter-impregnated polymer has at least two
Since it is composed of different types of monomers, it has a certain degree of compatibility with homopolymers made of any of these monomers. Thus, interimpregnated polymers tend to fuse to sheets or films made of conventional polymers of the monomers contained therein. In addition, since the mutually impregnated polymer has a crosslinked structure and a gel concentration, it will not melt as a whole and lose its shape even when heated. Therefore, the foamed particles obtained by foaming the inter-impregnated polymers are difficult to collapse the foamed structure and are stable in shape upon fusion, and are therefore suitable for use on molten films or sheets of common thermoplastic polymers. When the foamed particles are pressed from the inter-impregnated polymer onto the film or sheet, the foamed particles easily fuse onto the film or sheet without losing their shape. therefore,
Expanded particles made of interimpregnated polymers are suitable for fusing. Furthermore, the foamed particles welded in this way are difficult to crush, so they are suitable as a cushioning material.

In this method, the expanded particles described above are fused to a non-expanded film or sheet. Unfoamed films or sheets are conventional polymers obtained by polymerizing or copolymerizing the monomers that make up the interimpregnated polymer. For example, if the mutually impregnated polymer constituting the foamed particles is obtained by impregnating polyethylene with styrene and polymerizing it, the non-foamed film or sheet may be made of an ordinary polymer or copolymer of ethylene or styrene. Use coalescence. Here, the term "ordinary" is intended to exclude inter-impregnated polymers. That is, to make a non-foamed film or sheet, polyethylene, vinyl acetate, etc.
Ethylene copolymer, polystyrene, styrene α
- Use methylstyrene copolymer, etc.

Various methods can be used to make unfoamed films or sheets. In FIG. 1, the film or sheet is made by extrusion molding using an extruder, but various other known methods can be used, such as a method using a calender roll.

The foamed particles described above are sprinkled onto the unfoamed film or sheet while it is being heated and softened. The particles to be dispersed should be selected to be as uniform in size as possible. The particles are also distributed over the entire surface on one side of the film or sheet. To do this, particles are first spread in excess, and then particles not in contact with the surface of the film or sheet are removed. The particles are thus deposited in a single layer over at least one side of the film or sheet, resulting in a fused sheet as shown at 7 in FIG. The fused sheet 7 can be passed as it is through a cooling tank 8 and taken up by a take-up machine 9 to be used as a buffer sheet, which is the object of the present invention.

In FIG. 1, another film or sheet 6 is further fused onto the fused sheet 7 to form a laminated sheet 10.
This shows the mode in which this is done. Film or sheet 6
is extruded from another extruder 4, superimposed on the fusion sheet 7 while softened, and pressed by a press roll (not shown) to form the laminated sheet 10. The laminated sheet 10 thus produced is passed through a cooling tank 8 and taken off by a take-off machine 9. The laminated sheet 10 is, in other words, a buffer sheet that is the object of the method of this invention.

Although the above description uses an example in which no adhesive is used for fusion bonding, it is also possible to perform fusion bonding using an auxiliary adhesive.

The cushioning material obtained by the method of this invention is
It is as shown in FIG. When cylindrical expandable particles are used, the expanded particles also become cylindrical, and the flat surface of the expanded particles can be fused onto the surface of the film or sheet. The particles are fused over a large area onto the film or sheet and can be firmly integrated. Further, as a fusion sheet, as shown in FIG. 4, foamed particles can be attached to both sides of a film or sheet, and this can be used as a buffer sheet.

According to the method of this invention, since the foamable resin is foamed in the form of particles, it can be easily foamed.
The foamed resin can be uniformly expanded to a high magnification. In addition, since a mutually impregnated polymer is used as the resin, it has a crosslinked structure, so the foamed structure is difficult to collapse and is easy to fuse, which is convenient for fusion.
It is also less likely to be crushed and is suitable for use as a cushioning material. In addition, since a polymer obtained by polymerizing or copolymerizing the monomers constituting the mutually impregnated polymer is used as the non-foamed resin, it has an affinity with the foamed resin.
Therefore, they are easily fused and integrated. Therefore, according to the method of the present invention, it is possible to easily obtain a sheet having a good cushioning effect due to uniformly foamed particles simply by fusing the foamed particles. This invention provides such advantages.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the method of this invention. 2 to 4 are partially cutaway perspective views of a buffer sheet obtained by the method of the present invention. In the figure, 1 is an expandable particle made of mutually impregnated polymers, 2 is an expanded particle, 3 and 4 are extruders, 5 and 6 are films or sheets made of ordinary polymers, 7 is a fused sheet, and 8 is a cooling tank, 9 is a collection machine,
10 is a laminated sheet.

Claims (1)

[Claims] 1. Mutual impregnation obtained by polymerizing or copolymerizing a certain monomer, including another monomer in the polymer, and polymerizing the monomers in this state. Using a polymer and an ordinary polymer obtained by polymerizing or copolymerizing the monomers constituting the mutually impregnated polymer, the mutually impregnated polymer is impregnated with a foaming agent, and this is foamed in the form of particles. forming foamed particles, forming the above-mentioned ordinary polymer into a non-foamed film or sheet, and scattering the foamed particles on top of the softened film or sheet to fuse the particles to the film or sheet. A method for manufacturing a buffer sheet, characterized by: 2. The mutually impregnated polymer is obtained by polymerizing the certain monomer described above, forming the polymer into spherical or cylindrical particles, dispersing the particles in water, and adding the above-mentioned and other polymers containing a polymerization initiator. In this state, other monomers are polymerized, and an aliphatic hydrocarbon having 3 to 6 carbon atoms or a halogenated aliphatic hydrocarbon is added as a blowing agent to form expandable particles. A method for manufacturing a buffer sheet according to claim 1. 3. The method for manufacturing a buffer sheet according to claim 1 or 2, wherein the certain monomer is ethylene and the other monomer is styrene.