JPS6036132A - Sheet for formation of shrinkable sleeve - Google Patents

Abstract

PURPOSE:To provide an excellent shrinkability while being excellent in the usability by raising the rate of open cells over 40% in the cell structure by mainly employing a shrinkable foam polyolefin resin sheet. CONSTITUTION:A shrinkable foam polyolefin resin 1 made of polyethylene resin or the like is laminated on a shrinkable non-foam polyolefin resin film 2 made of a polyethylene resin or the like to form a sheet S for the formation of a shrink sleeve. A foam sheet 1 is molded by adding a foaming agent and other additives to a polyolefin resin comprising a low-density polyethylene and an ethylene acetatevinyl copolymer, a copolymer resin of these resin and a mixed resin thereof. The expansion ratio of the foam sheet 1 is adjusted by a foaming agent. Then, a core agent such as talc serving as foaming core works to change the generation ratio of closed cells and open cells. The use of the sheet S for the formation of a shrink sleeve can lower the shrinking temperature with a very large shrinkability under the heating as the foam 1 as main component exceeds 40% in the rate of open cells.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet for forming a shrinkable sleeve, and aims to provide a sheet suitable for use as a material for a shrinkable sleeve for covering and protecting glass bottles containing carbonated drinks and the like.

Conventionally, the outer surface of a glass bottle, etc. is covered with a sleeve made of a heat-shrinkable thermoplastic resin sheet, and the sleeve is shrunk by heating to cover the outer surface of the glass bottle, etc., so that it closely adheres to the outer surface of the glass bottle, etc., and when the glass bottle, etc. is transported and stored. I in! Efforts are being made to protect it.

In order to shrink and cover a glass bottle with a complicated uneven shape or constriction, it is better for the shrinkable sheet that forms and covers the sleeve to have a high shrinkability due to heat. Efforts have been made to improve the contractility of various types of seams used in the manufacturing process.

In this invention, improvements have been made to a foamed polyolefin resin sheet that has excellent flexibility and low Nj tIl so that it can exhibit excellent shrinkability as a sheet for forming sleeves and has excellent usability. Its composition is mainly composed of a shrinkable foamed polyolefin resin sheet, and the cell structure of the foamed sheet is characterized by a mixture of open cells and closed cells, and an open cell ratio of 40% or more. There is.

Next, embodiments of the present invention will be illustrated below with reference to the drawings.

(1) is a shrinkable foamed polyolefin resin made of polyethylene resin, etc.; (21 is a shrinkable non-foamed polyolefin resin film made of polyethylene resin, etc. similar to the above); both sheet (1) and film (2) Both have so-called heat-shrinkability, which means they shrink when heated, and they are laminated to form a shrinkable sleeve-forming sheet (S).

The above-mentioned shrinkability is imparted by stretching when the foamed sheet (1) and non-foamed film (2) are produced by extrusion molding, or by a subsequent stretching process after molding.

The foam sheet (1) is made of resins such as low density polyethylene, high density polyethylene, polypropylene, polybutene-1, ethylene vinyl acetate copolymer, copolymer resins of the above resins, and mixed resins of these resins. It is molded by adding a foaming agent and other additives to polyolefin resin.

Among the additives, ordinary volatile 11 physical foaming agents (butane, pentane, freon, etc.) are used as foaming agents, and the foaming ratio of the light absorption sheet (1) is adjusted by this foaming agent. Further, the above-mentioned foaming agent is also necessary for stretching the foamed sheet (1) to a thinner thickness.

Then, a nucleating agent such as talc, which serves as a foaming nucleus for foaming the above-mentioned foaming agent, or a nucleating agent, which serves as an auxiliary foaming agent that acts as the above-mentioned foaming nucleus and also acts as a foaming agent, is blended as an additive. Depending on the substance added as the nucleating agent, the structure of the cells formed in the foamed sheet (1), that is, the ratio of closed cells to open cells, changes.

In addition, to generate and cover open cells, a substance that generates carbon dioxide (COt) is used as a light extraction gas, and to generate closed cells, a substance that generates nitrogen gas (N2) is used as a foaming gas. use.

Specifically, as a substance that generates closed cells or a substance that generates nitrogen gas, an azo type such as azodicarbonamide (azobisformamide) is used as an organic foaming nucleating agent that is triblended with raw resin pellets or powder. material,
Sulfonyl hydrazide-based substances such as benzenesulfonyl hydrazide, hydrazide-based substances such as pt-toluenesulfonyl hydrazide, P-P'oxybisbenzenesulfonyl hydrazide, etc. are used, and nitrogen gas is also used directly in the middle of the extrusion molding machine. It can also be carried out by being press-fitted into the

The organic chemical foam nucleating agent may be added to the raw material resin of the foam sheet (1) in an amount of 2 parts or less; if it is more than this, the sheet will be colored yellow, which is not preferable.

Next, as a substance that generates open cells or a substance that generates carbon dioxide gas, sodium bicarbonate, ammonia carbonate, or Mu! I tp1i
'Hydrocellol (product name: manufactured by Ninin Nisseika Kogyo Co., Ltd.), which is a reactive substance of salts and weak acids, is used, and carbon dioxide gas is directly injected into the extrusion molding machine. It is also possible to implement it.

By appropriately adjusting the blending ratio of the above-mentioned nitrogen gas-generating substance and rArll+ gas-generating substance, foamed sheets h fil with various open cell ratios can be obtained.

Incidentally, even if only carbon dioxide gas is used, *Vc bubbles will be formed, but the bubbles will be rough and the smoothness of the sheet will be poor, so it is necessary to contain an appropriate amount of nitrogen gas as well.

The foamed sheet (1) having the above composition can also be used as a sheet (S) for forming shrinkable sleeves in Japan and Germany, but usually the foamed sheet h (11) is
By laminating non-foamed fill 1) (2) on this,
It is possible to improve strength, scattering resistance when the bottle is broken, printability, smoothness, etc.

The non-foamed film (21 is the foamed film 1-(
A polyolefin resin similar to 1, 1 is used, and the resin is added with an engineered f-lene vinyl acetate polymer (E
V△) Mix the resins in advance. This EVA resin is effective in improving the printability of the non-foamed film (2). The mixing amount is 1 to 1 in terms of VAIi in the entire resin component.
It can be used in an amount of 10% by weight, preferably 2 to 5% by weight.

If a white pigment such as titanium dioxide is used as an additive to be added to the non-foamed film (1), printability will be improved. In order to improve the dispersion of titanium dioxide into the resin, Qa-stearic acid, stearic acid, low molecular weight polyethylene resin, low molecular weight polypropylene resin, etc. are used in combination as a lubricant and a dispersant.

Other additives include various colorants, lubricants, antistatic agents, weathering agents (ultraviolet absorbers), etc.

A sheet for forming a shrinkable sleeve (S
), both sheets (1) and film (2
) is laminated and covered at the same time as molding by coextrusion, and there is a method in which the foamed sheet (1) and non-foamed film (2) are separately molded in advance and then laminated using adhesives, thermal bonding, etc. .

In the mass co-extrusion method, pre-melted resin for foamed sheet (1) and non-foamed film (2) are mixed in an extrusion mold.
) may be combined together with the resin and extruded at the same time, or a binding adapter may be provided between the extruder and the extruder before entering the mold to avoid integrating both resins.

Then, a predetermined elongation is obtained depending on the difference between the linear velocity of the melt in the mold and the drawing speed of the sheet, and the ratio of one die to the diameter of the drawing plastic. Heat shrinkability is imparted to the completed sleeve-forming sheet (S).

Note that the foam sheet (1) is made of polyethylene acid-resistant vinyl j1.
Since the melting point is low in the case of polyethylene resin, low-density polyethylene, high-density polyethylene resin, etc., the culm alone can provide sufficient stretching, and the sheet for forming the sleeve can have a large shrinkage property even at low heating temperatures. l'l can be given.

However, polypropylene, polybutene-1 resin, etc., which have a high melting point, exhibit large shrinkage at temperatures close to the melting point of ζ1, which is the extrusion scar, and have insufficient shrinkage at low temperatures.

Therefore, depending on the intended use of the sleeve, the molded sheet (S) may be heated again to a relatively low temperature and re-stretched to give it shrinkability (=l) at low temperatures. 2. Hot rolls, tenter rolls, etc. are used for the post-stretching process, and it can be carried out either by in-line processing continuously with the forming process or by separately processing in the outline.

Next, as a method different from coextrusion, there is a method in which foam sheets (
1) and the non-foamed film (2) are separately extruded to provide stretching (1) and shrinkability (1).

Shrinkable foam sheet 1-(1
) and the shrinkable non-foamed film (2), or
The sleeve-forming sheet (S) of the present invention can be produced by thermally adhering them with a contact layer in between.

In case of direct non-contact S, foam sheet (1)
Or a non-foamed film (preferably, it contains a resin component that improves mutual adhesion. Foamed film (2) Which material resin is most suitable for non-contact? 1 If the combination does not have good properties, or if there are required qualities such as particularly strong flJl'Jl resistance, or if there are restrictions on the operating conditions when using the sleeve. applicable in certain cases.

For example, an adhesive layer is required in the case of a combination of low density foamed polyethylene film I-1 and unfoamed polypropylene film or polybutene-1 film.

And the adhesive layer is made of ethylene acetate beer 11tt.
Various types of adhesive polymers can be used.

The sheet for forming a shrinkable sleeve (S) manufactured as described above has a cell structure in the foamed sheet (1) in which the open cell ratio is 40% among open cells and closed cells.
% or more.

” - Measurement of open cell ratio [Yomari ΔS1 ~ +1) -28
56 (Method C), measure the amount of i+l continuous bubbles in Sea I~, and measure the amount of resin part from the bottom of Sea 1~.

Then, in the above formula, m of the closed cell part is it LT-! Ill.

(Closed cell part) % = 100 - (open cell part) % - (resin part) %...
(1) The open cell rate or closed cell rate is calculated from this lp +.

(Ratio of open cells) % 1 ′″′ (Open cell portion) 10 (closed cell portion) × 100 ・・・・・・・・・(2) (Ratio of closed cells) % part) + (closed cell part) × 100 ...... (2)'a3 The open cell ratio above depends on the mixing ratio of the nucleating agent, the operating temperature during extrusion molding, the pressure point It also varies depending on the structure of the mold, and is not determined only by the blending ratio of the nucleating agent.

In addition, the sheet (S) for forming a shrinkable sleeve of the present invention has an overall thickness of 0.1 to 0.5 mm, and has a foaming (rX ratio of 12 to 5).
The shrinkage rate shall be 30% or more after heating at 130°C for 10 seconds (with the sheet in a free state).

And'' 2) - (SntJ, Foaming Sea 1 - +1
) is wound into a cylindrical shape with the inside facing, and both ends are joined to form a sleeve (Δ) (see Fig. 2).

This sleeve (A) is used for charcoal, beverage, etc.
[J (G) is covered, heat-shrinked, and the glass bottle (G) is protected by being tightly attached to the glass bottle (G) (see Figure 3).

According to the shrinkable sleeve forming sheet (S) of the present invention configured as described above, the foam sheet (1) becomes one piece.
The open cell ratio/i0% or more is 1J, and the shrinkage when heated is extremely large, 15! The degree of depletion can be lowered.

In other words, if the open cell rate is high, the life T1 for extrusion molding 11.1 is high.
Stretched during the stretching process from exit 11 to the top of the plug! , the sheet is easily fixed as it is, so the heating time is 11'l.
This improves the shrinkability of the material.

Because of its high shrinkability, it is easy to shrink-coat bottles with complex uneven shapes or "necks," and the shrinkage time is short and the shrinkage temperature can be low, making the coating process easy. Productivity can also be improved.

Due to the low cotton absorption, when printing is performed on the surface of the sleeve-forming sheet (S), a beautiful sillage can be obtained without causing appearance defects such as printing peeling and printing distortion.

Furthermore, if the bubbles in the foamed sheets 1 to (1) are open cells, it is easy to print on the non-photoelectric film (2) on the front side, which is effective in improving printability.

In addition, if the foam sheet (1) only has closed cells or has a high ratio of closed cells, a secondary foaming phenomenon will occur in the foam sheet (1) when the sleeve (A) is heat-shrinked, and it may not be sufficient for skin etc. Not only is it impossible to tightly cover the bottle, but the sleeve (Δ) also stretches along the axial direction of the bottle, resulting in the disadvantage that the end surface of the sleeve is not straight but curved.

These drawbacks could be overcome by increasing the open cell ratio.

Next, specific examples will be explained by showing precise data.

<Example-1> The foam sheet (1) was made of low-density polyurethane resin (
M I = 1.0++ / 10m1n, dense 13.
g = +1.922+]/CC) to 100 parts by weight, a heavy part to azodicarbonamide as a nucleating agent, 13 parts by weight of helium for hydrogen carbonate (the above △ and B tir)
, 1) and 1.0 parts of talc were uniformly mixed together in a 65φ extrusion chamber with 1/D=35, and heated and melted.

Then, in the middle of the extruder, 3 parts by weight of butane, which acts as a foaming agent, is press-injected and mixed.
1 (at 18 ka/h) 9 people discharged and foamed the 41 sheets, and then stretched them into a sheet using a 200φ mandrel.

In addition, as for the non-foamed film (2), low f, n Lσ poly-1 dylene (M I = 3.0 g / 10 m1n,
S, g" O, '1230/CC) 85 heavy lifting and engineering f1 non-vinyl citrate J (!i'I holiday (M I = 0
．． 68o/1 (1min, VAc = 15% by weight
1 part of titanium dioxide as a white pigment is uniformly blended into the mixed resin with 15 parts of titanium dioxide as a white pigment. this,
After being supplied to a 40φ extruder with L/D = 24 and heated and melted, extrusion m3 ka /
1", the foamed sheet (1) is introduced into the molten resin around the molten resin, extruded from the mold at the same time, and taken to the mandrel side to form a two-layer composite sheet for forming a shrinkable sleeve. A sheet (S) was obtained.

The above-mentioned sheet (S) was formed by laminating the foamed sheet (1) and the non-foamed film (2) firmly and could not be peeled off.

The non-foamed film (2) was white and opaque, and had a very smooth surface.

The correct measurement data for the above sheet (S) is shown in the table below.

Note) How to measure shrinkage rate: 100m
Insert a sheet section of m, and after heating for a specified time, measure the dimension of the sheet in the extrusion direction, and express the degree of shrinkage as a percentage: 1=
.

Note that Comparative Example 1-1 is an IC case except for sodium bicarbonate, and the open cell rate is low and the heat shrinkage rate is extremely small, making it unsuitable for use.

Moreover, Comparative Example 1-2 is a case in which azodicarbonamide is excluded, and the open cell ratio is 100% and the heat shrinkability is also good (r), but there is a drawback that the cells are coarse and lack smoothness.

<Example-11> In Example-I, the low-density polyethylene resin constituting the foamed sheet (1) and non-foamed film (2) was replaced with random polypropylene copolymer resin, and the detailed data are shown in the table below. Show.

Note) The method for measuring the thermal shrinkage rate is the same as in Example-I, but the temperature of the constant temperature bath was changed to 170°C.

In Comparative Example n-1, sodium bicarbonate was omitted, the open cell ratio was low, and the heat shrinkability was extremely low.

<Example-■> Differences from Example 1 will be explained in 1.

The foam sheet (1) is made of polypropylene resin (M
I = 1.0g/10m1n, S, o = 0
．． 90g/cc) 1.0% of Hydrocellol P-70 (trade name: manufactured by Koshu Seika Kogyo Co., Ltd.) per 100Φ weight part
A raw material resin uniformly mixed with parts by weight and 1.0 parts by weight of talc is supplied to a 65-φ extruder. Pressure-inject a butane pentagram as a foaming agent, and add 35k of nitrogen gas as a nucleating agent.
g4G and introduced into the coextrusion mold at an extrusion rate of 17 kg/H.

In addition, as the non-foamed film (2), high-density polyethylene 'J (MI = 0.5 (1/1ONn, S
, Q = 0.9501 / Cc) 85 weight fl) parts and vinyl acetate copolymer (M I = 0.6
(1/10m1n, VΔc-15@% content) 1
5 parts by weight of -19210 parts by weight of dioxide was uniformly blended into the mixed resin, and this was introduced into the co-extrusion mold through the 40φ extruder at an extrusion rate of 3 k(]/11 to form a shrinkable sleeve. A forming sheet 1-(S) was manufactured.

The obtained sheet (S) had a thickness of 0.33 ntm and an Iσ of 0.455 tll/cc, and the non-foamed film (2) was white, opaque, and had excellent smoothness.

In addition, the open cell rate was 75%, and the shrinkage properties were excellent.

[Brief explanation of the drawing]

The figures illustrate embodiments of the invention (1).
The figure is a sectional view, Fig. 2 is a perspective view of Three 1, and Fig. 3 is a sectional view of the bottle with shrink coating (-) (1)... Foam sheet, (2)... ... Non-foamed film, (S) ... Sheet for forming shrinkable three 1, (A) ... Sleeve, (G) ...
...Glass bottle. Patent Applicant: Tsukisui Chemicals 1'31 Co., Ltd. 1 Figure 1 Figure 2 Figure 1 2

Claims (1)

[Claims] 1. The foam sheet is mainly composed of a shrinkable foamed polyolefin resin sheet, and the foamed sheet has a cellular structure in which open cells and closed cells coexist, and the open cell ratio is 40% or more. A sheet for forming shrinkable sleeves. 2. The sheet for forming a shrinkable sleeve according to claim 1, wherein a shrinkable non-foamed thermoplastic resin film is laminated on one side of the shrinkable power generating polyolefin resin sheet. 3. The sheet for forming a shrinkable sleeve according to claim 1, wherein the shrinkable non-foamed thermoplastic resin film is a shrinkable non-foamed polyolefin resin film.