JPH04224928A - Heat sealing method for film or sheet - Google Patents

Abstract

PURPOSE:To heat fusion bond a film or a sheet composed of a polyolefin resin composition containing a large amount of a surface bleeding compound which is not heat fusion bonded by the heat sealing method heretofore available. CONSTITUTION:An emboss pattern of 5-30mum depth is formed on the surface of a film on a sheet composed of a polyolefin resin composition containing a large amount of a function imparting agent such as an anti-oxidizing agent and a surface bleeding compound as low-molecular polyolefin and then the film is heat sealed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for heat sealing films or sheets manufactured from polyolefin resin compositions, and the method is applicable to packaging bags for various articles, wide sheets used in architecture, civil engineering, agriculture, etc. It is used to manufacture back-in-boxes, simple gloves, plastic envelopes, etc. from films or sheets.

0002

2. Description of the Related Art A method of heating films or sheets made of polyethylene or polypropylene to a temperature above their melting point using a heat sealer to heat-seal the films or sheets together is a widely known and commonly practiced method.

However, in recent years, articles manufactured from polyolefin films or sheets have been used in a variety of industrial fields, and the performance and functions required have become diverse. or add various compounds to the polyolefin to give it functionality. For example, the molecular weight distribution of polyolefins may be broadened to improve mechanical, optical, and processing properties, in which case the amount of low molecular weight polyolefins is increased. Further, even when it is necessary to narrow the molecular weight distribution, a low molecular weight polyolefin may be arbitrarily produced due to restrictions on the polymerization catalyst and polymerization method. If a relatively large amount of low molecular weight polyolefin is generated in a high molecular weight polyolefin in this way, it may be extracted and removed using a solvent, but this will increase the cost, so it should be left as is unless it has a major adverse effect on the properties of the product. I am using it.

On the other hand, the performance of polyolefin itself cannot satisfy all the performance requirements of the end use. Fire additives, lubricants, plasticizers, crosslinking agents, brighteners, light stabilizers, heat stabilizers, processing aids, metal corrosion inhibitors, antifogging agents, anti-fog agents, colorants, anti-mold agents, freshness-preserving agents, Contains functional agents such as deodorants, water repellents, voltage stabilizers, and anti-tree agents.

[0005] These low-molecular-weight polyolefins and functional agents tend to bleed from the high-molecular-weight polyolefin matrix to the surface even in minute amounts due to differences in entropy and polarity. The present inventors have confirmed through experiments that even if it exists at the interface, it does not interfere with the thermal fusion between molten high molecular weight polyolefins, but when it is present in a large amount, it inhibits the thermal fusion between high molecular weight polyolefins.

[0006]

[Problems to be Solved by the Invention] As described above, films and sheets made from polyolefin resin compositions containing large amounts of surface-bleeding compounds such as low-molecular-weight polyolefins and functional agents are preferable in terms of function and performance. However, because it is difficult to heat-seal them, they could not be used for packaging bags, etc. The present invention was made to solve these problems, and it is a polyolefin resin composition that cannot be thermally bonded by a normal heat sealing method because a large amount of a surface-bleeding compound bleeds onto the surface. An object of the present invention is to provide a method for heat-sealing films or sheets manufactured from materials.

[0007]

[Means for Solving the Problem] As a result of intensive research, the present inventors have found that the surface bleeding compound present on the surface of the film or sheet can be thermally fused by a heat sealing method of a film or sheet manufactured from a polyolefin resin composition. We conducted a number of experiments on the correlation between the surface morphology of the film or sheet and the thermal bonding strength, and found that in the case of a specific surface morphology, surface bleeding compounds are present in large amounts. The present invention was completed based on the discovery that heat fusion is possible even when the material is heated.

That is, the method for heat-sealing a film or sheet of the present invention is a method for heat-sealing a film or sheet manufactured from a polyolefin resin composition containing a large amount of a surface-bleeding compound. It is characterized by having an embossed pattern with a depth of 5 to 30 μm.

[0009] In the above heat sealing method of the present invention,
Low molecular weight polymer whose surface bleed compound bleeds,
Antioxidants, antistatic agents, ultraviolet absorbers, far-infrared generators, flame retardants, lubricants, plasticizers, crosslinking agents, brighteners, light stabilizers, heat stabilizers, processing aids, metal corrosion inhibitors, antifogging agents. These compounds are selected from agents, anti-fog agents, colorants, anti-mold agents, freshness-preserving agents, deodorants, water repellents, voltage stabilizers, anti-tree agents, etc. Included are: 2,6-di-tert-butyl para-cresol, laurylstearylthiopropionate, 2-hydroxybenzophenone, (2'-hydroxyphenyl)benzotriazole, trilauryltrithiophosphite, chlorinated paraffins. , tetrabromoethane, sorbitan monofatty acid ester, ethylene oxide adduct of fatty acid, stearylamide, ethylene bistearoamide, montan wax, cadmium stearate, polyethylene oxide, phthalocyanine blue, polyethylene wax, dicumyl peroxide, polysiloxane, tetramethoxy Silane, γ-methacryloxypropyltrimethoxysilane, polysiloxane-oxyalkylene copolymer, vanillin, geraniol, flavonoids, low molecular weight polyolefins, etc.

[0010] The amount of these surface-bleeding compounds to be used in the present invention is within a range that exceeds the amount normally blended into polyolefin resin compositions and inhibits the thermal fusion of the film or sheet by the heat sealing method. is the amount used or present. For example, pentaerythritol tetrakis (β-laurylthiopropionate), an antioxidant used in high-pressure polyethylene films, does not ooze out onto the film surface at all when added at 0.1% by weight or less; Exceeding 5% by weight increases the amount of exudation, and at 2% by weight, the heat seal strength decreases by 10%,
% by weight makes heat sealing impossible. In addition, according to the method disclosed in Japanese Patent Application Laid-Open No. 59-230011,
Density is 0.91g/ml, melt index 0.9g
When an ethylene-butene-1 copolymer with a weight average molecular weight of 10,000 or less was produced, 8% by weight of the ethylene-butene-1 copolymer with a weight average molecular weight of 10,000 or less was produced. The heat seal strength was 0.2 kg/15 mm, indicating that the low molecular weight substance during polymerization inhibited the heat seal strength.

[0011] In the present invention, the method of forming an embossed pattern with a depth of 5 to 30 μm on the surface of a film or sheet is carried out by pressing the film or sheet between a chill roll and a pressure roll having an appropriate surface roughness. , whereby an embossed pattern is applied to the heat-sealed surface of the film or sheet. Types of embossed patterns include tortoise shell, lattice, silk, diamond, bead, linen, satin,
Spraying etc. is effective. However, the present invention is not limited to these, and includes, for example, a case in which concave portions and convex portions are continuous on a continuous line and valleys and peaks are formed alternately, and an improvement in heat sealing strength is also observed in this case.

[0012] Also, the embossing depth (JIS B060
1) is 5 to 30 μm;
If it is less than μm, the heat sealing strength is insufficient;
This is because the heat sealing strength is similarly insufficient even if the thickness is 0 μm or more. More specifically, the emboss depth is 5
At micrometers or less, the compound that bleeds onto the surface forms a relatively flat and thick surface layer, and when this is heat-sealed, the embossed convex parts of the polyolefin film are exposed, and the virgin convex parts are pressed together and heat-sealed. to prevent things from happening. On the other hand, at 30 μm or more, the polyolefin of the embossed convex portion is exposed by heat sealing, and the virgin convex portions are pressed together and heat-sealed, but the large value of the emboss depth means that the area of the entire film In contrast, the area of the convex portion is relatively reduced,
The area of the convex portions that are heat-sealed to each other is reduced, and the heat-sealing strength per area is reduced. On the other hand, in the range of 5 to 30 μm, which is the numerical range of the embossing depth in the present invention, the surface bleeding compound present at the interface between the heat-sealed surfaces of the convex portions is relatively reduced, and the film area is reduced. On the other hand, the area of the convex portion is relatively large, and both effects are well balanced and high heat sealing strength can be obtained. In addition, the embossing depth in the present invention is 15 to 2
5 μm is suitable.

In the present invention, polyolefin resins include high-pressure polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene- Vinyl alcohol copolymer, ethylene-carbon monoxide copolymer, ionomer, high density polyethylene,
Medium density polyethylene, polypropylene, propylene-α
- means an olefin copolymer, etc.

[0014]

EXAMPLES Next, the present invention will be explained in more detail based on examples. Examples 1 to 3, Comparative Examples 1 to 2 Ethylene-ethyl acrylate copolymer with ethyl acrylate content of 19% and melt index of 0.75 g/10 min (manufactured by Nippon Unicar, trade name WN-130) 100
Parts by weight, antioxidant pentaerythritol tetrakis (
After kneading 1.8 parts by weight of β-lauryl thiopropionate (manufactured by Cipro Kasei, trade name: Seenox 412S) at 160°C for 10 minutes using a Banbury mixer, the mixture was granulated to obtain pellets. A film with a thickness of 100 μm was produced from this resin composition in the form of pellets using a T-die, and the film was embossed with a satin pattern as shown in Table 1 below.
The embossing depths shown in Figure 1 were applied to various embossing depths, and after being left at room temperature for 3 months, heat sealing was performed (temperature 140°C, pressure 1kg).
/cm2, 1 second) to measure the heat seal strength. The results are summarized in Table 1. The heat-seal strength of the above film heat-sealed under the same conditions as above without embossing was 1.3 kg/15 mm immediately after film production, and 0.1 kg/15 mm after 3 months.
It was 15 mm.

Examples 4 to 6, Comparative Examples 3 to 4 JP-A-59-
According to the method disclosed in No. 230011, the density is 0.
．． 906g/ml, melt index 0.8g/10
From an ethylene-butene-1 copolymer having a weight average molecular weight of 60,000 and containing 15% by weight of a low polymer having a weight average molecular weight of 15,000 or less, a thickness of 8
Immediately after producing a 0 μm film, heat sealing (temperature 150° C., pressure 1 kg/cm 2 , 1 second) was performed, and the heat sealing strength was 1.5 kg/15 mm. Further, after the film was left at room temperature for 3 months, heat sealing was performed under the same conditions as above, and the heat seal strength was 0.2 kg/15 mm. On the other hand, immediately after the film was manufactured, it was embossed with a satin pattern at various embossing depths shown in Table 2 below, and after being left at room temperature for three months, it was heat-sealed under the same conditions as above. The heat seal strength was also measured. The results are summarized in Table 2.

[0016]

Effects of the Invention As explained in detail above, the film or sheet heat sealing method of the present invention is superior to the conventional heat sealing method by providing an embossed pattern with a specific range of emboss depth on the surface of the film or sheet. It has now become possible to heat-seal a film or sheet made of a polyolefin resin composition containing a large amount of surface-bleeding compound, which could not be heat-sealed in the previous method, without reducing the heat-sealing strength.

Therefore, according to the method of the present invention, polyolefins containing low molecular weight polymers and functional agents, which have excellent functions but have not been used conventionally because of their low heat sealing strength, and functional agents can be used. It is possible to improve the heat seal strength of films or sheets manufactured from polyolefin resin compositions containing a larger amount than the amount used, expanding the field of use of these films or sheets, and improving functionality and performance. Packaging bags for various items,
Alternatively, it is possible to manufacture wide sheets, back-in-boxes, simple gloves, plastic envelopes, etc. used in construction, civil engineering, agriculture, etc.

Claims (2)

[Claims] Claim 1: A method of heat-sealing a film or sheet produced from a polyolefin resin composition containing a large amount of a surface-bleeding compound, in which an embossed pattern with a depth of 5 to 30 μm is applied to the surface of the film or sheet. A method for heat sealing a film or sheet, characterized by: 2. The surface bleeding compound is a bleeding low molecular weight polymer, an antioxidant, an antistatic agent, an ultraviolet absorber, a far-infrared generator, a flame retardant, a lubricant, a plasticizer, a crosslinking agent,
Brighteners, light stabilizers, heat stabilizers, processing aids, metal corrosion inhibitors, anti-fog agents, anti-fog agents, colorants, anti-mold agents, freshness-preserving agents, deodorants, water repellents, voltage stabilizers 2. The method of heat sealing a film or sheet according to claim 1, wherein the heat sealing agent is selected from the group consisting of .