JPH01105739A - Skin packaging film - Google Patents

Abstract

PURPOSE: To obtain the superior deep drawability and high drawing ratio and to perform packaging by deformation without rupture by containing linear ethylene/α-olefin copolymer in a film. CONSTITUTION: A film includes polyethylene, and linear ethylene/α-olefin copolymer, the linear ethylene/α-olefin copolymer can be blended with one or more kinds of polymers. A copolymer of α-olefin and α, β ethylene unsaturated carboxylic acid or the like can be preferably blended, and the film has the antistatic property and the static elimination property. The film is made of a non-orientation material. In the case when the film is made of the orientation material, the inflation method is applied. As another method, a plurality of support layers are simultaneously extruded, and the layers are coated or laminated. The obtained film has about 20:1 or more drawing ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particular film as a skin packaging film for high profile and/or heavy articles, food or non-food. More specifically, the film comprises a linear ethylene/α-olefin copolymer. In a preferred embodiment, the film comprises:
Antistatic or static dissipative properties
ipative) and can be used to skin-wrap static-sensitive devices such as circuit boards.

Skin packaging is essentially a vacuum forming process. In a typical method, a sheet of thermoplastic film is placed in a frame with a vacuum plate below the frame and a backing plate above the vacuum plate.
A piece of gas permeable support, such as a g board) is placed. The product to be skin wrapped is placed on top of the support plate and heat is applied to the thermoplastic film within the frame. Once the film is heated until it is sufficiently soft, the frame is lowered and the plastic sheet self-trapes onto the product. When trapping occurs, a partial vacuum is created through the vacuum plate and the air beneath the plastic film is extracted through the support plate. The pressure difference between the top and bottom of the plastic sheet presses the sheet tightly around the product. The support is adapted to adhere to the plastic sheet. Typically, the film can be adhered to the support by heat, or the film can be coated with glue, or the support plate can be so coated.

When the two come into contact with each other, a strong bond occurs, resulting in a package in which the product is held snugly to the support for safe transportation and subsequent field display at the retail point.

Vacuum skin packaging differs from the skin packaging methods described above in that the thermoplastic film and support are gas impermeable and the resulting package can be evacuated and optionally hermetically sealed.

The same end result is desired. That is, the product should be held leaktight to the support plate by the film.

Vacuum skin packaging methods generally use a vacuum chamber with an open top. The product on the impermeable support plate is placed on a platform within the vacuum chamber. The top of the chamber is then covered with a sheet of film, which is tightly clamped to the chamber to form a vacuum closure. The film is heated to the forming and softening temperature and the chamber is evacuated.

The platform can then be raised to force the product onto the softened film (dr 1ve) and air pressure can be applied over the film to force the film tightly around the product.

The conventional method is to make a porous support plate or a gas permeable plate with holes so that a vacuum can be drawn directly through the support plate;
A support plate is used.

As used herein, the term "vacuum" refers to vertical pressure (
differential fluid pressure
re), in which case the fluid may be either gas or liquid. “Skin packaging” as used herein
The term is intended to refer to the vacuum packaging method described above, regardless of whether the support is permeable or impermeable. Typically, the support is made from cardboard coated with an adhesive polymer, so that
The film sheet will adhere as the sheet is heated and traced onto the article to be skin wrapped and a pressure differential is applied.

Various patents describe skin wrapping machines and methods. Representative patents include French Patent No. 1.258,
No. 357 (Bresson) (March 6, 1961), French Patent No. 1,286,018 [Laroch Freres, Ltd.
)] (January 22, 1962), Australian Patent No. 245,774 [Colpro Proprietary
Limited (Colbro Proprietary L
td) and Cole and Son Proprietary Limited.
etary Ltd)] (1196377116, U.S. Pat. No. 3,491.504 (Young et al.) (1970
U.S. Pat. No. 3,545,163 [Mahaffy et al] (1
Dec. 8, 970), U.S. Patent No. 3,694.991
(Perdeu et al.) (October 3, 1972), and U.S. Pat.
August 27, 985). The disclosures of these patents are incorporated herein by reference. However, the films of the present invention can be used with various films such as VS-44, marketed by the Cryovac Division of W.R. Brace, or PORT-A-VAC, marketed by AmPak. It is noted that it can be used with other types of skin packaging machines. The films of the present invention are not intended to be limited to skin packaging using only the machines described herein.

The skin packaging method causes the excess portion of the film to form an undesirable wrinkle upon evacuation, and the packaged material or article becomes irregular in shape, thus giving rise to a poor appearance. Furthermore, packaging films are prone to tearing at folded and wrinkled areas. As the film becomes thinner during the vacuum skin packaging process, conventional films
It is true that due to insufficient tensile strength and insufficient elongation, the material to be packaged has a tendency to break at certain protrusions or depressions that are randomly located when subjected to high stretching or drawing ratios. It was confirmed by conducting a test. Breaks can occur during packaging or during subsequent handling of the packaged product. Therefore, both the method and the film are unfavorable from a practical point of view.

Therefore, there is a strong need for improved packaging films and methods.

Conventional low density polyethylene (LDPE) is typically used for skin packaging, and attempts have been made in the past to provide certain improved skin packaging films. For example, U.S. Pat. No. 4,275,544 [Hisazumi et al., Kureha et al.
Assignee] (June 30, 1981) discloses an improved vacuum packaging method using a specific laminate film as the packaging film, which laminate film is It consists of a plastically deformable layer of synthetic resin having a yield stress of more than 50 kg/am' and an elongation at the elastic limit of more than 40% at a molding temperature of 50°C to 180°C. U.S. Patent No. 4,375.851
No. [Transferee to Beims Howros (Pa)]
uros) discloses a skin packaging material consisting of a thermoplastic material with reinforcement consisting of strands (in the form of a net or all extending in one direction parallel to each other). , the material is heated to a forming temperature for skin wrapping around the article on the support, such that upon exposure to a heat source at suitable time intervals, both the film and the strands are heated to a forming temperature for skin wrapping around the article on the support; When heated equally, it has less extensibility than film. The above US patent teaches that the strands flare out of the article at the base of the article in such a way as to provide a wider base of support for the article and prevent the film from becoming too thin. Skin packaging for articles using the material is also disclosed. It is also known from U.S. Pat. No. 4,590,741 [Long et al., Assignee to General Dynamics]] to skin-wrap static sensitive articles with three-layer films; are heat-sealable electrically semiconducting polyethylene (se
mi-conductive polyet, byle
ne) and an intermediate layer sandwiched between the first and second outer layers and adhered to the first and second outer layers; The layer is lXl0'
Oichimu/CM! The intermediate layer is impregnated with a sloughable electrically conductive material that provides the interlayer with a volume resistivity of less than This is prevented by the first or second semiconducting polyethylene layer.

It is therefore an object of the present invention to provide a film suitable for skin packaging of products, which has high tensile strength and elongation properties even at high stretch or draw ratios, so that it does not break. The object is to provide a film that is sufficiently deformable to conform by deformation to the shape of high profile and/or heavy products to be packaged. In other words, this film has excellent deep drawing properties and gives a high drawing ratio. Another object of the invention is to provide a skin packaging film for packaging high profile and/or heavy products with high antistatic properties. One aspect of this film is that it can also be used as a material for packaging items that typically have sharp protrusions, such as meat bones, electronic components, and the like. Films according to the invention typically also have good see-through properties, which is advantageous for reading code numbers preprinted on products packaged with this film. This film exhibits very good adhesion to the substrate, especially thermal adhesion when the substrate is Surlyn-coated cardboard.

Accordingly, the present invention provides a skin packaging film comprising a linear ethylene/a-olefin copolymer.

The present invention comprises a support of a material capable of adhering a polymeric film to one side of the support, an article on that side of the support, and a polymeric film comprising a linear ethylene/me olefin copolymer. We also offer skin packaging consisting of:

The invention comprises: a) placing an article to be packaged on a support;
b) disposing a film array of linear ethylene/α-olefin copolymer on said article and support [L, c) heating the film, d) evacuating gas from the space between said film and said support, and A method of skin packaging is also provided, comprising e) sealing the film to the support.

The present invention also provides skin packaging films comprising linear ethylene/α-olefin copolymers that are suitable for skin packaging high profile or heavy items.

The present invention comprises a support of a material capable of adhering a polymeric film to one side of the support, an article on that side of the support, and a polymeric film comprising a linear ethylene/me olefin copolymer. It also provides skin packaging, characterized in that the film is sufficiently deformable to allow high profile or heavy items to be skin wrapped with the film.

The invention comprises: a) placing an article to be packaged on a support;
b) placing a film over the article, C) heating the film, d) drawing a vacuum between the film and its support, and e) drawing the film over and around the article. A method of skin packaging is also provided, characterized in that the film is heat-sealed to a support, the film comprising an antistatic linear ethylene/α-olefin copolymer film.

The present invention also provides an antistatic skin packaging film comprising an antistatic ethylene/alpha-synthetic fin copolymer.

The film of the invention is characterized in that it has a high draw ratio of about 20=1 or higher and can therefore be used for skin packaging of high profile articles.

The film of the present invention has excellent drawing ratio and extensibility (str
etch) and is sufficiently deformable so that it can be used for skin wrapping high profile and/or heavy items. "Heavy" means about 10 bonds (about 22 kg) or more, more preferably about 1
It is intended to mean having a weight of 5 pounds (about 33 kg) or more, more preferably about 20 bonds (44 kg) or more. A "high profile" refers to an article having a vertical:minimum horizontal dimension ratio of about 20:l or greater, such as an article that is substantially perpendicular to the support (i.e., substantially vertical ) direction about 20
Intended to mean an essentially cylindrical article having a height of inches (50,8 cm) and a base diameter of about 1 inch (2,5 cm) in a direction substantially horizontal to the support. . This film has excellent deep drawability.
draw) of about 20:1 or more, more preferably about 25:1 or more, particularly preferably about 30
= 1 or more vertical dimension of the article: skin packaging of the article with a drawing ratio of the minimum horizontal dimension. In a preferred embodiment as described in Example if) below, the deep deep draw ratios are about 64:1.
It is.

The conventional LDPE is 16 as seen in Table 111B below.
:1 can be used, but as shown in Table ■C below, 26:
It splits in l. Of course, the films of the present invention can be used to skin-wrap smaller weight articles or shallow profile articles, if desired.

The film of the present invention comprises polyethylene, linear ethylene/α
- Comprising an olefin copolymer.

The linear ethylene/α-olefin copolymers can be blended with one or more suitable other polymers. Other suitable polymers are discussed further below. Regarding the linear ethylene/α-olefin copolymer of the present invention, “6-linear low density polyethylene” (LLDPE)
The term refers to compounds whose molecules consist of long chains with a small number of side branches or crosslinks obtained by low-pressure polymerization, e.g. butene-11pentene-1,4-methyl-pentene-11
C, -C, such as hexene-1, octene-1, etc. α−
Refers to modern copolymers of ethylene and one or more comonomers selected from olefins. The side rods present are short compared to non-linear polyethylene. Although the molecular chains of linear polymers can intertwine, the forces that tend to hold the molecules together are physical rather than chemical and are therefore weakened by energy applied as heat. sell. Linear low density polyethylene preferably has a density ranging from about 0.911 g/cc to about 0.928 g/cc for film manufacturing purposes. The melt flow index of linear low density polyethylene generally ranges from about 0.1 to about 10 g.
/10 minutes, preferably in the range of about 0.5 to about 3.0 g/10 minutes. Linear low density polyethylene resins of this type are commercially available and are produced by low pressure gas phase and liquid phase processes using transition metal catalysts. Very low density linear low density polyethylene (VLDPE) can be used and such typically has a density of about 0.910
g/cc to about 0.860 g/cc or even less.

Suitable other polymers that can be blended with linear ethylene/α-olefins include, but are not limited to, polyethylenes other than linear ethylene/α-olefins, ethylene vinyl acetates, and ethylene alkyl acrylates. It's not something you do. Polyethylene with a density ranging from about 0.900 g/cc to about 0.928 g/cc is referred to as low-density polyethylene (LDPE); Polyethylene is called medium density polyethylene (MDPE) and is about 0.941 g/cc to about 0.940 g
Polyethylene with a density of /cc is called high density polyethylene (HDPE). The earlier classical low density types of polyethylene are usually polymerized at high pressures and high temperatures, and the earlier classical high density types are usually polymerized at relatively low temperatures and pressures. Ethylene vinyl acetate copolymers (EVA) are formed from ethylene and vinyl acetate monomers, with the ethylene-derived units in the copolymer being present in a large amount and the vinyl acetate-derived units being present in a minor amount in the copolymer. For film forming purposes, the vA content of the EVA is preferably from about 3% to about 25%.

The reason is that when EVA has higher VA content,
This is because EVA behaves like glue or adhesive. Ethylene alkyl acrylate copolymer (FAA) is
Refers to a copolymer formed from ethylene and an alkyl acrylate, in which the ethylene-derived units are present in a large amount and the alkyl acrylate-derived units in the copolymer are present in a small amount. Therefore, "perethylene-methyl acrylate copolymer" (EMA)
The term refers to a copolymer formed from ethylene and methyl acrylate monomers. The term ``ethylene-ethyl acrylate copolymer'' (FAA)
Refers to a copolymer formed from ethylene and ethyl acrylate monomers. The term "ethylene-butyl acrylate copolymer" (EBA) refers to a copolymer formed from ethylene and butyl acrylate monomers. Many suitable EBAs are commercially available and have a butyl acrylate content of about 3% to about 18% by weight.

Copolymers of the formula RHC-CH2 (wherein R is H or CI Cm alkyl) with .alpha.,.beta. ethylenically unsaturated carboxylic acids and the like are also suitable for blending. Preferably, in the RHC-CH2 copolymer of olefin and carboxylic acid, the olefin is ethylene and the carboxylic acid is acrylic acid or methacrylic acid. α-olefins of the formula, RHC=CH2 (wherein R is H or C, -C, 7Jl/kill) and α
, a copolymer with a beta-ethylenically unsaturated carboxylic acid, can be one of the Nucrel (TM) polymers typically supplied by DuPont, or manufactured by Midland, Michigan. Dow·
Primacol (supplied by Chemical Kanhoney)
Primacor (TM) polymers. These are produced by copolymerization of ethylene with carboxylic acid comonomers such as acrylic acid or methacrylic acid. Formula, RHC-CH2 (wherein R is H or C
The copolymer of an a-olefin (I Cm alkyl) with an a,β ethylenically unsaturated carboxylic acid can also be a metal salt neutralized with, for example, sodium, Na.

Thus, the copolymer can be an ionomer.

Typically, such ionomer materials are manufactured by Surfy from E.I. du Pont de Nimoas & Co., Wilmington, PR
n) (TM) and is available commercially as U.S. Patent No. 3.355.319 and U.S. Patent No. 3.84.
No. 5,163 describes this in detail.

In a preferred embodiment, the film is antistatic or static dissipative and can be used for skin packaging of static sensitive articles such as circuit boards. Nevertheless, the film of this embodiment is suitable for pork, red meat (r.
It is also suitable for skin packaging of other products that do not require antistatic protection, such as ed meat), cottage cheese cartons, boxed toys where one side of the box is open to view the toy through the plastic film skin packaging, etc.

In antistatic embodiments, the polymer is about 20% by weight.
More preferably, it contains up to about 15% by weight of one or more antistatic agents.

Antistatic agents are generally several orders of magnitude larger than the conductivity of the polymer (polymers are typically good insulators).
increase. No special method is required to incorporate the antistatic agent into the polymer; any well-known wet blending, melt blending or tri-blending method can be used.

This antistatic aspect is due to the static charge reduction of the polymer film containing the antistatic agent.
decay), ie, the ability to dissipate static charges. The film of the polymer containing the antistatic agent is subjected to a direct current of ±5000 volts for a short period of time, i.e., no more than 20 seconds, more preferably no more than 5 seconds, and most preferably no more than 2000 milliseconds. 99% of static charges can be dissipated.

The U.S. Department of Defense (DOD) and the Electronics Industry Association (Electrical Association)
onics Industry As5ociatio
n(E I A) each has its own measure for the surface resistivity of the material in ohms/square as follows:

DOD larger than 10"1014~to' 10
'～to' Smaller than to' EIA Larger than 10"
1013~10' As can be seen from 10', there are two major differences. One is that the EIA defines insulation as approximately 1013 ohms/square or higher.
In contrast, the DOD defines insulation as greater than about 10'' ohms/square. The other difference is EIA
is that the antistatic property is within a range of about 1013 ohms/square to about 105 ohms/square,
This means that antistatic property is synonymous with static electricity dissipation property. On the other hand,
DOD is about 1 OI4 ohms/square to about 10' ohms/square for antistatic properties and about 10' for static dissipative properties.
It is divided into two separate ranges from 9 ohms/square to about 105 ohms/square. The literature, especially older literature, often equates antistatic properties with static dissipative properties when discussing static electricity.

Thus, as used herein, the term "antistatic" refers to materials having a surface resistivity (Department of Defense standard) in the range of about 109 to 10'' ohms/square, and/or preferably 20 to 10'' ohms/square. 99% of the applied electrostatic charge of ±5000 volts DC for a short time period of less than 2 seconds, more preferably less than 5 seconds, and most preferably less than 2 seconds (2000 milliseconds)
Materials capable of dissipating [Federal Test Method Standard 101]
c.

Method 4046. l “Electrostatic properties of materials” (Fe
deral Te5t Method 5tan
dard l01c, Method 4046
゜1 ”Electrostatic Property
ies of Materials") 1 and/or a material with a surface resistivity in the range of about 10' to 1013 ohms/square (Electronic Industries Association standard).

In a preferred embodiment of the present invention, the antistatic agent is (a) 1
(b) fatty acid esters of one or more polyhydroxy alcohols, (b) one or more I! More polyalkoxylated compounds (i.e. polyethers), such as polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetramethylene oxide, reaction products of long chain acids with polyalkoxylates, polyhydroxyl alcohols (e.g., polyalkoxylate reaction products of long chain acids, fatty glycols, fatty sorbitols, fatty sorbitans, and fatty alcohols), or (a) ) and (b). Suitable long chains in either (a) or (b) are desirably from about 08 to about C20 or higher. The polyether chain in a suitable polyalkoxylated compound has the formula (-0CXH2X)n, where X is from 2 to about 8, the alkyl group is linear or branched, and n is 2. from about 1000 to about 1000. The multidrugs act singly in the polymer composition,
Although such compositions exhibit superior static decay times, the combination of (a) and (b) in polymeric compositions is desirable because these antistatic compositions exhibit even shorter static decay times. Desirable fatty acid ester-substituted polyhydroxy alcohols include ethylene glycol, 1.3
-Propylene glycol, 1,2-propylene glycol, 1,2-butanediol, meso-2,3-butanediol, l,4-butanediol, pinacol, pentaerythritol, 1.2,3.4.5-pentane Polyhydroxy alcohols selected from CxC* alcohols such as pentol, sorbitan or sorbitol, where these polyhydroxy alcohols are substituted with one or more fatty acid ester groups are included. , but not limited to these. A highly desirable fatty acid ester substituted polyhydroxy alcohol is glycerol monostearate (GMS).

A preferred polyether is polyethylene oxide (P
EO), for example, trade name Polyox.

X) Polyethylene oxide, sold by Union Carbide under the trade name, or polytetramethylene oxide, such as polytetramethylene oxide, sold by DuPont under the trade name Terathane. Highly desirable polyalkoxylates of fatty alcohols have the formula, C16H'330 (
C2H40)IH (wherein n is 2 to about 50)
polyethoxylated cetyl alcohol (PECA) as represented by Highly preferred antistatic films comprising linear ethylene/α-olefin copolymers include GMS, PE○ and PECA.

Advantageously, the mixture of polymer and antistatic agent also includes a small amount, up to about 10% by weight, and more desirably up to about 7% by weight, of antiblocking agent to alleviate tactile tackiness. . A suitable antiblocking agent is Thyroid, which is present in EPE 8160 supplied by Teknor Apex.

The film can be manufactured as follows. The film can be formed from a non-oriented material, or if formed from an oriented (i.e. heat-shrinkable) material,
"'hotblown" technique
The inflation method (“trapped bubble” technique), better known as
que) can be formed from a tube. In forming hot blown films, the tube is first stretched with hot blown bubbles essentially immediately after extrusion while the tube is still at an elevated temperature above the orientation temperature range of the material.
tch). The film is then cooled using known methods. Those skilled in the art are well aware of this method and the fact that the resulting film has substantially non-oriented characteristics. Other methods for forming unoriented films are well known. Examples thereof are slot die extrusion or cast extrusion (cas), which are also well known to those skilled in the art.
This is a plane method of texture. If an oriented or heat-shrinkable film is desired, the thermoplastic material, heated above its pour or melting point, from an extrusion die or co-extrusion die is generally processed into, e.g., tubular or planar (sheet) form. Production can be carried out by extrusion (single-layer films) or co-extrusion (multi-layer films) in the form, followed by cooling after extrusion. Stretching of the orientation pool can be performed while the film is still hot in its orientation temperature range at some point during cooling, followed by completion of cooling. Alternatively, after post-extrusion cooling, the relatively thick "tape" extrudate is then reheated to a temperature within its orientation temperature range and stretched to orient or stretch the crystallites and/or molecules of the material. "Oriented" or "heat-shrinkable" material is herein defined as a material that, when heated to a suitable temperature above room temperature (e.g., 96°C), exhibits a change in shape in at least one linear direction. Defined as a material having a free 5hrink of 5% or more.

Various other methods for forming films are well known to those skilled in the art. For example, the conventional ripening method or layering method (
laminating technique) can be used. For example, multilayer support layers may first be coextruded through inflation tubes and then additional layers may be extrusion coated or laminated thereon, or two multilayer tubes may be coextruded and one of the tubes may be extruded through the other. may be extrusion coated or laminated over.

As used herein, the term "extrusion" or "extrusion" is intended to encompass extrusion, coextrusion, extrusion coating, or combinations thereof, whether by tubular methods, planar methods, or combinations thereof.

Optionally, the films of the present invention can include a barrier layer. The barrier layer is made of vinylidene chloride copolymer (
or preferably at least about 50%, most preferably about 99%
or a layer comprising a hydrolyzed ethylene vinyl acetate copolymer (EVOR), or both a layer comprising a vinylidene chloride copolymer and a layer comprising EVOH. can become. When the barrier layer comprises a layer comprising EVOH, the mole percent vinyl acetate prior to hydrolysis should be at least about 29%.

This is because at lower amounts, the effectiveness of the hydrolyzed copolymer as a barrier to fluids such as gases is substantially reduced.

The barrier copolymer generally has a melt flow comparable to that of the other components of the multilayer film, preferably in the range of about 3-10 (melt flow is generally an ASTM
D1238) is further preferred. The gas of primary concern is oxygen, and the permeability through the barrier material is 70cc/m''/mil thickness/24 hours/measured according to ASTM method D-1434.
If the pressure is below atmospheric pressure, the transmittance is sufficiently low, i.e.
The barrier material is considered to be relatively gas impermeable. EVOH can be advantageously used in the films of the present invention. The reason for this is that the high-energy electron irradiation treatment of the completely coextruded film
This is because the barrier layer is not deteriorated. In the case of vinylidene chloride copolymer barrier layers, deterioration can be slow. As stated in this section, this reference to gas ``impermeability'' of barrier polymers such as Saran or EVOH is intended to be a reference only to the barrier polymer.

This is not intended to be a reference to the gas "impermeable" properties of one type of support used in skin packaging as described above. However, in skin packaging applications, it may be desirable to use a barrier polymer film as the support.

Irradiation is not necessary as very suitable films exhibiting good deep drawability and high drawing ratios are obtained without irradiation. Optionally, irradiation crosslinking can be performed using high energy electrons, ultraviolet light, X
This can be achieved by using radiation, gamma rays, beta particles, etc. Preferably, up to about 20 megarad (MR) doses of electrons are used.

The irradiation source can be an electron beam generator operating in the range of about 150 kilovolts to about 6 megavolts, with a power output capable of providing the desired dose. The voltage is, for example, 1. It can be adjusted to OOO, OOO or 2,000,000 or 3,000,000 or 6°ooo, ooo or any suitable level l which may be higher or lower. Many other devices for irradiating films are known to those skilled in the art. Irradiation is typically performed at a dose of about IMR to about 20 MR, with a preferred dose range of about 2 MR to about 12 MR. Irradiation can conveniently be carried out at room temperature, but higher and lower temperatures, for example from 0°C to 60°C, can also be used.

Additionally, it will be appreciated by those skilled in the art that irradiation with high-energy electrons is generally detrimental to saran barrier layer compositions, as the irradiation degrades and discolors the saran, turning it brownish. ing.

Therefore, when high-energy electron irradiation is performed on a film with a barrier layer, including a saran layer, after complete coextrusion, the irradiation should be carried out with care at low levels. Alternatively, this situation can be avoided by using extrusion coating.

Therefore, by extrusion coating, first the first layer (1
(or co-extruded), subjecting that layer to high-energy electron irradiation, and then coating a Saran barrier layer, for which the outer surface of the extruded previously irradiated tube is coated with a saran barrier layer. Other subsequent layers (which may or may not be irradiated) are extrusion coated simultaneously or sequentially. This sequence allows the first step without exposing the saran barrier layer to its deleterious discoloration effects.
The layer(s) and subsequent layer(s) are subjected to high-energy electron irradiation.

Crosslinking of polymers, as is well known to those skilled in the art,
It can also be done chemically through the use of chemical crosslinkers.

For example, crosslinking agents such as organic peroxides or dialdehydes have been used to crosslink polyethylene polymers and copolymers.

A general description of chemical crosslinking is provided by John Wilay & Sons.
Polymer Science and Technology, Plastics, published by , Inc.) and copyrighted 1966.
Encyclopedia of resins, rubber and fibers
a of Polymer 5science and
Technology, Plastics, Re5
Ins, Rubbers, Fibers), Volume 4, pages 331-414.

Referring to FIG. 1, there is schematically shown an article 5 skin-wrapped onto a support 3. As shown in FIG. The article is of rectangular cross-section in the direction horizontal to the support. Support 3 is Surlyn coated cardboard with holes (not shown). The film 4 extends from the top 2 of the article 5 down to where part l of the film covers the support 3.

Referring to FIG. 2, a pencil IO with a sharp tip 9 is placed on the support 6 with the tip 9 facing away from the support 6 and with the end of the eraser adjacent to the support 6. It is schematically shown that 6 is skin-wrapped by a film 7. Also shown is some web 8 of film 7 about two-thirds of the way down from tip 9.

Example The following examples illustrate preferred embodiments of the invention.

It is not intended that the invention be limited thereby.

All percentages given in the examples are by weight, but
The amount of Polyox is so small that it is expressed in parts per million (ppm).

The following substances were used in the examples.

TrycolXTM 5984 is manufactured by Emery Industries.
polyethoxylated cetyl alcohol (PECA) supplied by ies).

Food grade (GMS) glyceryl monostearate 1-CP
H-53-N is C.P.*-R ((:.

P. Hall).

Alathon F-3445 is EVA with about 3.5% vinyl acetate. It was supplied by DuPont.

Daw XU 61512.08L is a VLDPE supplied by Dow. The comonomer is octene, the melt index is 0.80 and the density is 0.905.

Dowlex (TM) 2045
, 04 is a linear low density polyethylene supplied by Dow Chemical Company of Midland, Michigan. It has a density of 0.920±0.002, the comonomer is octene, and the melt index is 1.1. Hereafter, for convenience, this will be referred to as LLDPE,04.

Dowlex(TM) 2045.03 is a linear low density polyethylene supplied by Dow Chemical Company of Midland, Michigan. That is 0.920
, the comonomer is octene, and the melt index is 1. It is 1. From now on, for convenience, this will be referred to as L.
It is called LDPE, 03.

Chemplex 3404 is an LDPE supplied by Chemplex Company of Loring Meadows, Illinois.

EPE8160 transparent thick anti-blocking agent is 90% by weight LD
PE (Dow Resin 722) and 10% by weight Thyroid (S
micron-sized silica (micron 5ized 5ilica) which is a blend with yloid) 378
It is. This Thyroid is Techno-Apex (Te
Infrared opaquefier supplied by Aknor Apex.

Polyox(TM) is a polyethylene oxide (PEO) sold by Union Carbide Toni.

Example 1 National Rubber φ Manufacturers (Nati
onal Rubber Manufacturers
) supplied by a pacemaker
r) A 2° mil (0.51 mm) thick film having the following composition was produced using the method of slot die extrusion with a 3.5 inch (8°9 cm) slot die extruder.

Table ■ Ingredients (%) Percentage LLDPE, 04 98.5) PE
GA 1.0) 90%) GMS
O, 5) ) 100% PEO
200ppm)) EPE8160 10%) Next,
Using a skin packaging machine supplied by AmPak, the following articles were skin wrapped with the above film using Surlyn coated cardboard support board as the support.

a) 2 pieces with a length of 9 inches perpendicular to the cardboard
-7/8" x 5" x 9" wood block. The aperture ratio was approximately 3.1:1.

b) 2 inches thick in the vertical direction to the cardboard f-
2 inch x 4 inch x 8 inch lead brick
brick), and the aperture ratio was approximately 0.5:l.

C) A 3-5/8 inch diameter x 4-3/4 inch high cylindrical soda can measuring 4-3/4 inches vertically to the cardboard, with a drawing ratio of approximately 2.3:l. there were.

d) 5 inches thick in the vertical direction to the cardboard
The circuit board was inch wide x <inch thick x 6 inches long, and the drawing ratio was about 12:l.

e) Height perpendicular to cardboard 4. 〉2 with inches
- <inch diameter x 4> inch height capacitor. This capacitor had a multi-inch tall pin connector with many vertically pointed pins. The aperture ratio is approximately 1.
The ratio was 7:1.

f) A pointed wood block of 1/8 inch diameter x 8 inch height with a height of 8 inch to the cardboard. The aperture ratio was approximately 64=1.

g) A pocket knife approximately 3/16 inches by 6-3/4 inches high with a vertical height of 6-3/4 inches relative to the cardboard. The exposed blade pointed upwards. Aperture ratio is approximately 36
=1.

h) A 2 inch x 2 inch x 2 inch inductor can with a thickness of 2 inches perpendicular to the cardboard. This cancer had a pin pointing up.

The aperture ratio was approximately 1=1.

For all of these, the films were observed to pull well over sharp edges and corners during skin packaging, exhibiting excellent deep draw strength and elongation. The film is
Did not tear during skin packaging. This is particularly true of a pointed wooden cane (woo
den 5tick). The wrapped lead brick was turned over and held upside down several times. Although the bricks weighed approximately 26 pounds, 10 ounces, the film held the bricks tightly together, providing excellent strength for wrapping heavy items and not tearing. Ta.

Example 2 The film of Example 1 was tested for its antistatic properties. The ability of each sample to dissipate electrostatic charge was determined by Federal Test Method Standard 101c, Method 4046.1, “Electrostatic Properties of Materials” (
Federal Te5t Method 5tanda
rd 1OIG, Method 4046.1. “E
Electro-static Properties
of Materials”) (October 8, 1982
Electik Systems, Inc. (elect) using the method described in
A static decay meter, such as the 406C static decay meter supplied by Rotech Systems, Inc.
It was measured with Samples were equilibrated at about room temperature for about 24 hours at a relative humidity of about 15% or less, except where indicated.

After equilibration, each was 72'-73'F (22-23
℃) and charged to ±5000 VDC (volts direct current) at a relative humidity of less than about 15%. The time for 99% of the charge to dissipate was then measured.

Table ■ Sample Decay Time (milliseconds) Film itself Film skin wrapped around 725 wood block 1585** Decay time was tested from the tall axis to the side of the package.

Example 3 Several 4 mil thick monolayer films were extruded using the hot blow process described above. These films were as follows.

Table II [A Film Polymer EPE8160 Irradiation (I
JR) At VLDPE 90% 10%
None A2 VLI) PE 90% 10%
6A3 VLDPE 100%
None A4 VLDPE 100%
6BI LLDPE, 0390% 10%
None B2 LLDPE, 0390% 10%
6B3 LLDPE, 03100%
None B4 LLDPE, 03100%
6CI LDPE 90% 10%
None C2LDPE 90% 10% 6C3L
DPE 100% None C4LDPE 1
00% 6DIEVA 90%
10% None D2 EVA 100% 1
0% 6D3 EVA 100%
None D4 EVA 100%
6 Next, various articles were skin wrapped using an Ambax skin packaging machine. For drawing ratios below 7:1, a stack of cubic blocks was used, and for drawing ratios above 10:1, a hard plastic cylinder was used. Approximately 1 inch x 1 inch x 1 inch (approximately 2.5 cm x
Regular children's wooden cube blocks measuring 2.5 cm x 2.5 cm were skin-wrapped in Surlyn-coated cardboard with various films. The blocks were chosen because their vertical stacking easily correlates to the appropriate drawing ratio. That is, a stack of five blocks had an aperture ratio of approximately 5:1. However, 10
With an aperture ratio of :l, the Ambac machine did not have enough headroom to continue with the block, so a hard plastic cylinder was used. The deep drawability for a particular drawing ratio is described as poor (the film tears), good (the film does not tear but does not draw tightly to the base), or excellent (the film draws tightly to the base and does not tear). A score was given. Adhesion is determined by the relative cardboard fiber bond engulfment (re) of the Surlyn-coated cardboard into the film when the film is pulled from the Surlyn-coated cardboard.
lative cardboard fiber bi
nding evolution). The results are summarized in Table II [B.

ω
Dimension <
■

DEEP Sonoichi Deep non-comparison Di 3:1 4:l X 5:I X Comparison D2 3:1 4:1 5:1 7:l Comparison D3 3:1 4:l :1 5:1 7:l *NT = Not tested □-” NT Insufficient, few fibers are bonded X NT X NT NT Insufficient, few fibers are bonded X NT
LLDPE and LDPR (film samples Al to A4)
However, EVA (Samples Di to D4)
) were only good or unsatisfactory. Therefore, the deep drawability of the linear ethylene/α-olefin film of the present invention was superior to that of EVA. LLDPE,
For LDPE and EVA, irradiation also improved adhesion to Surlyn coated cardboard.

Next, it is shown that the linear ethylene/α-olefin films of the present invention are superior to conventional LDPH films. Pencils (similar to those shown in Figure 2 but not sharpened) were vertically skin-wrapped with VLDPE, LLDPE, and LDPE (rather than EVA).

The pencil had a diameter of approximately 0.29 inches (approximately 0.74 cm) and a height of approximately 7.5 inches (19.1 cm). The blunt end of the pencil was furthest from the cardboard and one end of the eraser was adjacent to the cardboard.

The sea urchin rubbing occurred about half way down the pencil path.

The results are summarized in Table II[C below.

DEEP Deep drawing performance film Deep drawing ratio Wang Tudan Ai Hong Ri At
26: I A2 tree 26:1 A3 26: I A4 book 26: I Bl 26: I 82 tree 26: I B3 26:1 B4 tree 26: I CI attempt 26: l XC 2 attempt Mit:
26:l X C3 attempted 26:l X 04 attempts! =26:l x 6M
B to irradiated Surlyn-coated cardboard with R Adhesion performance K Sticky but no fibers K Some fiber entrainment K Adhesive but no fibers X Some fibers and cardboard peeling K Very moderate fiber entrainment Some fiber entrainment X Very moderate fiber entrainment All of the skin-wrapped pencils were angled about 20° to 30″ from the cardboard base support.

Without wishing to be bound by any theory, this
This is likely due to the fact that the irradiation made the film tougher so that instead of the pencil remaining essentially vertical, the film pulled on the pencil.

All the LDPE film samples (C1 to C4) exhibited poor deep drawability and tore open at the attempted drawing ratio of 26:■, whereas the VLDPE film samples (AI to A4) and the LLDPE film The samples (B1 to B4) showed excellent deep drawability at a drawing ratio of 26:1. Therefore, the linear ethylene/α-olefin film of the present invention was superior to conventional LDPE.

Although representative embodiments and details have been shown for illustrative purposes,
Many modifications may be made to the embodiments described above without departing from the disclosed invention.

The main features and aspects of the invention are as follows.

1. A skin packaging film comprising a linear ethylene/α-olefin copolymer.

2. The above l having an aperture ratio of about 20:1 or higher
The film described in.

3- The tlA-like ethylene/α-olefin copolymer is blended with a polymer that is compatible with the linear ethylene/α-olefin copolymer, and the polymer is blended with an ethylene/alkyl acrylate copolymer, high density polyethylene (HDPE), low Density polyethylene (
LDPE), ethylene/vinyl acetate (EVA), ethylene/propylene copolymer, and the formula, RHC=CH
2 (wherein R is H or C, + C, alkyl) copolymers of α-olefins and a, β ethylenically unsaturated carboxylic acids, and mixtures thereof.
The film described in.

4. The film according to item 1 above, further comprising a barrier layer.

5. The film of item 1 above, wherein the film is irradiated with a dose of up to about 20 MR.

6. A support of a material adapted to adhere a polymeric film to one side of the support, an article on that side of the support, and a polymeric film line comprising a linear ethylene/α-olefin copolymer. Equipped with skin packaging.

7. a) placing the article to be packaged on a support, b) placing a film of linear ethylene/α-olefin copolymer on said article and the support, C) heating the film, and d) placing the film on the support. and e) sealing the film to the support.

8. A skin packaging film comprising a linear ethylene/α-olefin copolymer and suitable for skin packaging high profile or heavy articles.

9. A support of a material adapted to adhere a polymeric film to one side of the support, an article on that side of the support, and a polymeric film comprising a linear ethylene/α-olefin copolymer. skin packaging, characterized in that the film is sufficiently deformable so that high profile or heavy items can be skin wrapped with the film.

10. An antistatic skin packaging film comprising an antistatic linear ethylene/α-olefin copolymer.

11. The antistatic film of claim 10, wherein the film is sufficiently deformable so that high profile or heavy articles can be skin wrapped with the film.

12. The linear ethylene/α-olefin copolymer comprises (a) one or more fatty acid esters of polyhydroxy alcohols, (b) one or more polyalkoxylated compounds, or (a) The antistatic film according to IO above, wherein the antistatic film is blended with one or more antistatic agents selected from a mixture of and (b).

13, 1tff linear ethylene/α-olefin copolymer is blended with glycerol monostearate, polyethoxylated cetyl alcohol and polyethylene oxide. Antistatic property as described in 10 above. 11. The antistatic film as described in 10 above, which is capable of dissipating an applied direct current charge in about 2000 milliseconds or less.

15. a) placing an article to be packaged on a support, b) placing a film over said article, C) heating the film, d) drawing a vacuum between the film and the support, and e) drawing the film over and around the article to form a heat seal with the support, and f) said film comprising an antistatic linear ethylene/α-olefin copolymer. , a skin packaging method for packaging static sensitive articles.

16. The method of claim 15, wherein the film is sufficiently deformable so that high profile or heavy items can be skin wrapped with the film.

17. The la-type ethylene/,-olefin copolymer comprises (a) one or more fatty acid esters of polyhydroxy alcohols, (b) one or more polyalkoxylated compounds, or (a) 16. The method according to 15 above, wherein the method is blended with one or more antistatic agents selected from a mixture of and (b).

18. The method of claim 15, wherein the linear ethylene/α-olefin copolymer is blended with glycerol monostearate, polyethoxylated cetyl alcohol, and polyethylene oxide.

19. The method of claim 15, wherein the film is capable of dissipating an applied charge of ±5000 volts DC in about 2000 milliseconds or less.

20. A support of a material adapted to thermally bond a polymeric film to one side of the support, an article on that side of the support, and comprising an antistatic linear ethylene/α-olefin copolymer. A skin packaging comprising a polymer film comprising:

[Brief explanation of the drawing]

FIG. 1 is a schematic illustration of a skin-wrapped high profile article of rectangular cross-section in the direction horizontal to the support. FIG. 2 is a schematic representation of a skin-wrapped high profile pointed pencil. In the drawings, l...part of the film, 2...top of the article, 3...support, 4...film, 5...
Article, 6... Support, 7... Film, 8 Web,
9...Sharp tip, lO...Pencil.

Claims (1)

[Claims] 1. A skin packaging film comprising a linear ethylene/α-olefin copolymer. 2. a support of a material to which a polymer film can be adhered to one side of the support; and an article on that side of the support;
A skin package comprising a polymer film comprising a linear ethylene/α-olefin copolymer. 3. a) placing the article to be packaged on a support, b) placing a film of linear ethylene/α-olefin copolymer on said article and the support, c) heating the film, and d) placing the film on the support. and e) sealing the film to the support. 4. A skin packaging film comprising a linear ethylene/α-olefin copolymer and suitable for skin packaging high profile or heavy items. 5. a support of a material to which a polymeric film can be adhered to one side of the support; and an article on that side of the support;
The present invention comprises a polymeric film comprising a linear ethylene/α-olefin copolymer, the film being sufficiently deformable so that high profile or heavy articles can be skin wrapped with the film. Features skin packaging. 6. An antistatic skin packaging film comprising an antistatic linear ethylene/α-olefin copolymer. 7. a) placing the article to be packaged on a support, b) placing a film on said article, c) heating the film, d) drawing a vacuum between the film and the support, and e. a) drawing the film over and around the article to form a heat seal with the support; and f) said film comprising an antistatic linear ethylene/α-olefin copolymer. Skin packaging method for packaging static sensitive items. 8. A support of a material to which a polymer film can be thermally bonded to one side of the support, an article on that side of the support, and a polymer comprising an antistatic linear ethylene/α-olefin copolymer. A skin packaging comprising a film.