JPH03281341A - Multilayer heat sealable polypropylene film - Google Patents

Abstract

PURPOSE: To upgrade strippability, adhesive properties by adhering a heat sealable outer layer in the same range onto an upper surface of a core layer, adhering the outer layer in the same range onto a lower surface of the core layer to form a heat sealable multilayer film. CONSTITUTION: The heat sealable multilayer film A in which a heat sealable outer layer A and an outer layer C are laminated via a core layer B, the layer A is adhered to an upper surface of the layer B in the same range, and the layer C is adhered to a lower surface of the layer B in the same range is molded. The layer A is constituted by a heat sealing resin blended with one or more types of a slip agent noncompatible with a polypropylene, and the layer B is constituted by a heat sealable resin blended with a slip agent noncompatible with a polypropylene. The layer C is constituted by an isotactic polypropylene containing almost no slip agent.

Description

DETAILED DESCRIPTION OF THE INVENTION (A field of professional application) "Non-explosion" has good slip resistance and good adhesion to water-based adhesives such as water-based acrylic resin, Urtan resin and vinylidene chloride polymer (PVDC). Regarding multi-layer, heat-sealable polypropylene films.

BACKGROUND OF THE INVENTION Polypropylene films have a number of desirable properties, including excellent optical properties such as clarity ratio and gloss, satisfactory mechanical properties such as tensile strength and Young's modulus, and virtually non-toxic and odor-free properties. Equipped with special Hv. Polypropylene films are therefore widely used as packaging materials, especially for food products, but one of the drawbacks of polypropylene films is that they are poorly heat-sealable. In order to eliminate this, it is widely known to laminate a low temperature heat seal resin on one or both sides of a polypropylene film by coating, laminating or coextrusion. Heat-sealable resins of this type include, for example, medium and low density polyethylene, ethylene-propylene copolymers, hinithelene, butene and propylene terpolymers.

Another disadvantage of unmodified polypropylene films is that they exhibit relatively low slip notes.

That is, they exhibit a high inter-film friction coefficient.

This makes it difficult to use in such automatic packaging devices. One thing is that the slip weight of the film is low.

Processing equipment (e.g., heat sealing machines, bag making machines, bag loading equipment, bag openers - overwrap packaging) that would prevent automatic processing equipment from operating properly and reproducibly. In order to overcome the problem of slippage in heat-sealable films, the VC film must pass freely through the equipment.

181 or several conventional slip agents, such as oleamide, stearic acid, erucamide, etc., are commonly included in the heat seal adhesive film.

Crystalline polypropylene films exhibit relatively low vapor transmission properties, especially for oxygen or moisture.
For applications where films are used to package products such as food products that are attacked by these chemicals, it is often desirable to further enhance the gas or vapor barrier properties of the film. It is recognized in the art that one effective means for providing gas and vapor barrier protection for oriented polypropylene films is to coat such films with a polymer of vinylidene chloride.

When coating a polypropylene film with a vinylidene polymer composition, it is possible to ensure proper adhesion of the coating layer to the polypropylene support in automotive applications. For example, in many packaging applications, it is necessary to heat seal the covering film to itself or to other films to form a closed package. If the coating is improperly adhered to the support film, the package is likely to open prematurely when subjected to processing stress.

In order to obtain proper adhesion of the water-based adhesive to the polypropylene film surface, the film surface may be subjected to well-known pretreatment operations such as corona discharge, fire 2 or 1'! .

It must be treated with chemicals for oxidation.

This is common knowledge in this technical field. Another widely used method for improving the adhesion of water-based adhesives is to coat the surface of the polypropylene film with a special Brimarch coating, or to co-laminate the polypropylene film with an adhesion promoting film. be. However, both the coating method or the co-layering method involve an additional processing step, which increases the processing cost of the film.

If the polypropylene film contains a slip agent such as erucamide, the adhesion of the water-based adhesive to the polypropylene film surface is often unsatisfactory, even by pre-treatment of the polypropylene film, for example by corona discharge. This divine slip agent plumes or migrates to the surface of the polypropylene film,
Therefore, the effect of significantly increasing the bond between the film and the landing agent is ktJ.

(A Problem to be Solved by the Invention) Therefore, there is a need for a polypropylene film that runs well in a packaging machine and forms good adhesion with a water-based adhesive. Therefore, there is a strong need for a film that exhibits both a low coefficient of friction and good adhesion to aqueous adhesives, and that can be produced in a single processing step.

(Means for Solving the Problems) The present inventors have discovered that low friction coefficient, acrylic horse chestnut resin,
We have found a multilayer heat-sealable polyglobylene film that exhibits good adhesion to urethane resins and water-based adhesives containing PVDC and can be manufactured in a single processing step. This Yuzu film structure is essentially a heat-sealable outer layer (A
), core I-fBl and outer 11G).

The heat-sealing outer layer tAI is attached to the upper surface of the core layer (B) in the same range, and the outer layer 1G) is attached to the lower surface of the core layer (B) in the same range.

The outer layer IAI is formed essentially from a polymer composition (a) consisting of a heat-sealable resin blended with one or more slip agents.

The core layer 1011' is essentially derived from a polymer composition (b) consisting of an isotactic polypropylene homopolymer blended with one or more slip agents, and the outer layer 1011' is essentially a slip agent. A polymer composition (formed from C1) consisting of an isotactic polypropylene homopolymer substantially free of agents.

At that time, the key to the slip agent in the film structure is
The outer layer (A
It is effective to give the outer surface of l, but the substantial − of the structure
It is insufficient to cause any damage.

Due to the presence of the slip agent in the heat-sealing layer tAJ and the migration of the slip agent from the layer IB+ to the surface of the layer (Al), the outer layer IAI has a low coefficient of friction, which contributes to the excellent mechanical suitability of the film of the present invention. can get.

Since the slip agent is incompatible with polypropylene, it does not substantially migrate to the surface of the outer layer 1c+ and therefore does not interfere with good film-water ald adhesive bonding.

Accordingly, the present invention relates to the above-mentioned mini film and the above-mentioned film coated with a water-based adhesive.

The isotactic polypropylene homopolymer of the core FiilB+ and the outer layer tC+ is preferably t'! 0
．． 88-0.94 t/CC (880-940kf/F
Fg”) density and 230°C/2.16 Kp/
1 to 1 at z2 (0,0745 N/m') (pressure)
0F/10 minutes (1,67x10-6 ~ 16.7 x 1
0=kp/s) (measured according to ASTM D 1238).

The heat seal ratio of the outer layer IAI may be any of the copolymers, homopolymer friends, and blends of copolymers and homopolymers conventionally used for this purpose. Examples of heat-sealing copolymers that can be used in the heat-sealing layer are those listed below. About 1.5 to about 10. Ethelene-globylene copolymers preferably contain from about 3% to about 5% ethylene, copolymers of propylene and butene-1 containing from about 5 to about 40% butene-1, and from about 1 to about 10. Preferably about 2% to about 6% ethylene, about 80% to 97%. Preferably 1 unit about 8
8 to about 95 Mc1% propylene, and about 1 to about 20
．． Preferably from about 2 to about 15 dosage percent butene-15c'[
Ethylene-propylene-butene-1 terpolymer core # (B1) and heat-sealable #1 AJ are formed from a polymer composition containing a slip agent that is compatible with polypropylene. Slip agent in multilayer constructions The proportion of the slip agent must be sufficient to give the outer surface of the outer layer tAl a sufficient coefficient of friction for high speed heat-seal package operations, but not sufficient to result in substantial deformation of the film structure. Although best determined by the desired results, the additive is applied to the entire film structure in an amount of from about 0.02 to about 0.20, more preferably from about 1 to about 0.025 to about io, io. In a preferred form, the slip agent in the polymer composition forming the core layer (Bl) is preferably contained in the core layer (Bl), and the slip agent in the polymer composition forming the layer IAJ' is preferably contained in More preferably, the content of the composition forming the core layer (B) Y - nislip agent is about 400 to 800 ppm.
In both cases, the slip agent is preferably erucamide.

The slip agent in the core layer IB) leaches from IIIB) through the heat seal supination 1ml Al to the surface of the film by 1 blooming'' as known to those skilled in the art.

In this way, the additives present in the core IillBl are added to the layer I
On the surface of the AI, a state is obtained which favorably affects the coefficient of friction and the anti-blocking properties of the film structure. The slip agent preferentially blooms into the TAI layer, thus IcI 1
It is not present on the outer surface of the homopolymer of m and does not adversely affect the lamination bond.

Generally, the outer surface of the outer layer IAI has a coefficient of friction (ASTMD 1894) of about 0.45 or less, preferably about 0.35 or less at room temperature.
) 1f: Indication "f+."

Slip agent 1 that can be used in producing the film of the present invention
Those which are incompatible with evoliglobylene, ie, those which bloom to the surface from the core layer and the skin layer. This yuzu additive is known to those skilled in the art. Non-toxic surfactant injection agents, such as amides and carboxylic acids, are particularly useful. Preferred amides are those of carboxylic acids containing at least 5 carbon atoms, such as behenamide, lyrunamide.

Arachitamide, Ricinolabad, Palmitamide 2
myristamide, linolamide, lauramide, cabramide, pelargonamide, caprylamide, oroamide, stearamide.

N,N'-ethylenebisoleoamide, a highly preferred slip-shaving erucamide.

Useful carboxylic acids #I include those containing at least 4 carbon atoms, such as butyric acid, cabroic acid, caprylic acid, capric acid, lauric acid, laurolenic acid.

myristic acid, myristoleic acid, pentadecanoic acid,
Valmitin tIi, halamide oleic acid, margarine, stearic acid dioleic acid, lilunic acid, lyrinic acid, ricinol [, 2,3-dihydroxystearic acid, 12-hydroxystearic acid, behe7 acid, eleostearic acid , arachidic acid, 2-eicosanoic acid, 2.4-
Eicosagenoic acid.

These include 2-tocosenoic acid, 2-tetracosenoic acid, 2.4.6-titracosatrienoic acid, and the like.

The slip agent is preferably tri-blended with a polypropylene resin in the layer (Bl) or a heat-sealable resin in the layer IAI, and then melt mixed. It is also possible to prepare a highly concentrated Mivux, which can then be diluted to an appropriate proportion by adding turmeric.

Outside! Component C) preferably contains one or more anti-blocking agents from Keikyusha; Heat Seal 1iitAI also preferably contains an anti-blocking agent. Does it contain any of these?
Preferred antiblocking agents for σ are particulate free family members having an average particle size of about 0.5 to 5 microns. Some commercially available silica (Kaopolite)1
152, obtained from Kaoborite Co., Ltd., has an average particle size of 0.8 microns, while others (Siper-nat
) 44, available from Degussa Chemical Company, with an average particle size of 4.0 microns, any material or mixtures thereof can be used. Metal silicates, silica glasses, clays and other finely divided inorganic materials are also used. Viscous N inhibitor 1';! It is preferably present in an amount of about 0.05 to 0.5 to 1%, preferably about 0.1 to 0.6% by weight of 1N and/or (C).

It is preferable to include crystalline wax in the outer layer tAl of the heat seal. This is because by including it, much less wrinkling slip agent can be used than if it were not included, thus resulting in a film with a clean appearance and improved physical agility. This is because slip agents such as amides give the film a distinctive appearance.

Useful waxes may be any of the known copying waxes. However, it is preferred to use synthetic n-paraffinic waxes. Preferably 1 evax is about 85
It has a melting point of ~135°C. The wax is preferably added at about 5% to about 15% of the heat seal a layer, most preferably about 10% of the heat seal a layer. and other monoglycerides, which preferably contain about 0.05 to 0.03% of the 11, 1%, most preferably about 0.1
It is contained at a concentration of 1%.

The multilayer film of the present invention can be produced using any commercially available system for coextrusion of resin. Holimer composition ta1. Preferably, ibl and IcI are coextruded with each other. Bring the polymer to a molten state 1
It is coextruded from a regular extruder through a flat extrusion die. The melt streams then coalesce in an adapter before being extruded from the die. After exiting the multi-layered film rthI orifice, it is cooled and the quenched sheet is preferably reheated, e.g. by a factor of 4 to 6 at about 121°C (250'F) in the machine direction and then e.g. transversely. The film is stretched 8 to 10 times in the direction at about 160°C (320F). The outer layer 101'if preferably treated with flame or corona to provide at least 66 dynes/cn1
(36 mN/m), preferably 40 dynes/cm (4
0 mN/m) surface activity. Trim the edges of the film and roll the film tx5rc. The structure thus produced was heated to 37-52°C (100-125°F
It is preferable to condition or equilibrate by holding for up to 3 days to promote surface migration of the sliving agent to reduce the umbrella coefficient.

Since the above films have a low coefficient of friction,2 which allows them to be used in automatic packaging equipment, they also have good bonding with the flame or water-based adhesive on the Ecorona-treated surface of the outer layer (1C), i.e. Approximately 80-1505F
The film described above is advantageous because it is capable of forming a bond (measured with an Instron tester, pulled in the bond 'Kk direction) of (0.08-0.15 kg).

The composition of the water-based adhesive is not critical to the practice of the invention. Commercially available acrylic resins, urethane resins, and vinylidene chloride latex can be used. Generally vinylidene chloride content is at least 50%, preferably +S from about 75% to
Approximately 92% commercially available vinylidene chloride latex is used. Other eteV7'e+ unsaturated comonomers include α, β-
Ethylenically unsaturated acids, such as acrylic acid and methacrylic acid;
esters such as methyl methacrylate, ether acrylate, bunal acrylate, etc. In addition, α,β-ethylenically unsaturated nitriles, such as acrylonitrile and methacrylatetrile, are also used, as are monovinyl aromatic compounds, such as sunalene and dihibinyl.

Details of vinylidene chloride polymer latex: 82% vinylidene chloride, 14% enal acrylate
% by weight, and 4% by weight of acrylic acid. Or about 80% vinylidene chloride.

A polymer latex consisting of about 17% by weight methyl acrylate and about 6% by weight methacrylic acid may also be used.

Form 1, which the present inventors believe is currently the best for carrying out the present invention, is a film having the following structure.

IAI heat seal a.m: 90% propylene/ethylene/butene-1 monopolymer and 10% microcrystalline wax; erucamide approx. 1600 p1)m;
Glycerin monostearate (Myvale)
verol) 1806. (obtained from East '77 Chemical Company) approximately 110,001) p, as well as antiblocking agent silica particles (Syloid).

W, ) (obtained from Brace Co., Ltd.); tJ3+=+A1iii: Engineering A/Kaamide 400-
Isotactic polypropylene containing 800 ppm'r; 10) Outer layer: antiblocking agent silica particles (Cypernat 44) with an average particle size of about 0.8 microns, about 2400 p.
antiblocking agent silica particles (chaobolite 1152) with an average particle size of about 4,0 microns and about 3000 pI) m
isotactic polypropylene containing; the outer surface of this layer is corona treated to about 40 dynes 7 cm (40 mN/m ) K.

The invention is further illustrated by the following examples.

Example 1 Six types of films 5ffH were produced by the following method.

The manufacturing method consisted of coextrusion with an outer layer (~ and a 1 m IB+ core made of 101 k isotactic polypropylene. The core resin was
) 8670C (containing Ercamidoke) and 2 tons of standard isotactic non-Ercamido polypropylene. 7;) ), melt the JAI layer.

Coextruded with core 1- and fc1 layers. lc1 layer is 2
400 ppm Cybernat 44 and 3000 pI
) was an isotactic polypropylene containing chaoborite antiblocking agent particles. tAlj! 1 was extruded in the same way, containing 90% Chisso terpolymer (propylene/ethylene/butene-1, handcrafted from Chisso) and 10% σ bacrocrystalline wax, and a total of 1600 ppm erucamide, 11000 ppm charge Inhibitors meiverol and 6
iooppm antiblocking agent particle thyroid.

The three-layer extrudate was quenched and heated to approximately 121°C (250″
F) was stretched 4 to 6 times in the machine direction. Next, this longitudinally stretched sheet) was stretched at about 160°C (320°C) in the transverse direction by 8 to 1°C.
It was stretched 0 times. , 1011 so2 flame or 1'j corona to about 40 d/cm (40 mN/m) K, and wound into a mill roll. Next, this film 2
Stored at 37-52°C (100-125″F) for 1-3 days to promote surface migration of erucamide.

Film 1-A-This film 1, a normal 0>35%
Heat-sealed layers of random ethylene/globylene copolymer and I-? of isotactic polypropylene without erucamide or other slip additives.
It was a two-layer film containing This film is made of homopolymer 0tll Y corona treated, PVDC (Molton (
Morton) 2015].

Film 1-B - This film had the following three-layer structure. Outer layer + 1 + propylene/ethylene/butene-1 copolymer 50% 1 normal 3.5% consisting of 40% random ethylene/propylene copolymer, and 10% microcrystalline wax and anti-blocking and slip agents; core 1 (11) Erucamide 400-700
1) Normal isotactic polypropylene containing pm Y: and a heat-sealable outer layer (90% i+il propylene/ethylene/phthene-1 terpolymer, 10% microcrystalline wax and slip and antiblock agents.

Layer +Hv: +o treatment, PVCD (Gr
ace) 860CI).

Film 1-c - This film 1-e outer layer (11 is 100% isotactic polypropylene and 3000% isotactic polypropylene)
Outside the dotted line was the same as Film 1-B consisting of ppm C Chaoborite 1152 and 2400 ppm Cypernat 44 antiblocking particles. Homopolymer f@>
-xo treated and coated with PVDC (Brace 8600).

2.54 cnt (1 inch) strips 7 of the above product 1
The bonding strength of each laminate was examined by cutting it out and testing it with a tension tester. Alternatively, the Salater assay can also be used to measure smvij-binding. Custom made films 1-A, 1-B and 1-C are shown in Table 1.

No/i n 0.7-1.0(k
g/m) (0,028-0,039) -B 54/in 0.25-0.45 (kq
/m) (0,0098-0,018) -G? /in 0.25-0.35(ky/
m) (0,0098-0,014) a, hand layer 100-400 (3,9-15,8) 0-150 (O8 9-5.9) 0-150 (6,2 -5,9) Table 1 shows the data for films 1-A and 1-BfJ.
''-Indication that it is unacceptable-Fufilm 1
-Although A1 showed acceptable saran bonding strength, its #
The friction coefficient was too high for packaging machining suitability. The friction coefficient that can be accepted by 1-81 films has been shown, but it is 70 PV.
The film of the present invention (Film 1-C), which had too large a variation in DC bond strength, exhibited both saran bond strength before acceptance and 1 yarn bv after acceptance. The film on the T surface had satisfactory wetting marks and f.1 marks.

Example 2 Invention Q] Film! ! - What is the general method mentioned by Shio II I VC to show the defects of a film that has no texture? Other films were produced using the same method.

Film 2-A This Q film is a three-layer film with a core of isotactic polypropylene without additives and a heat-sealable lantum copolymer or terpolymer. Silicone oil was added to these two outer layers to provide lubricity.

Film 2-B □ This film has S'1ABA structure, and the core layer (B) G'! Erucamide 2000 ppm
Each IAI layer was a conventional 6.5% random ethylene/propylene copolymer.

The characteristics of these films are shown in Table 2.

Table 2 2-A (y/in) 0.50-0.40
0-25 (h4/m) (0,01
2-0,016) (0,98)2-B(j'
/in) 0.20-0.50 2
0-100 (kf/m) (0,0079-0
,020) (0,79-3,9)a, laminating the film itself The data in Table 2 shows that film 2-A has a good coefficient of friction, but has significantly poor PVDC bonding.
Film 2-B) shows a good coefficient of friction, but its PV
There is too much variation in DG binding. These examples clearly show that the erucamide in the outer layer tC+ needs to be kept to a minimum and that enough of the erucamide on the other surface is needed to obtain acceptable packaging machine processability. Make it.

(4 other people)

Claims (1)

[Claims] 1. A heat-sealable outer layer (A), a core layer (B), and an outer layer (
C), the outer layer (A) is attached to the upper surface of the core layer (B) in the same area, and the outer layer (C) is attached to the lower surface of the core layer (B) in the same area. (i) The outer layer A is formed from a polymer composition (a) mainly consisting of a heat-sealable resin containing one or more slip agents incompatible with polypropylene; (ii) ) The core layer (B) is derived from a polymer composition (b) mainly consisting of an isotactic polypropylene homopolymer blended with one or more slip agents incompatible with polypropylene; (iii) the outer layer ( C
) is formed from a polymer composition (C) consisting primarily of isotactic polypropylene homopolymer with substantially no slip agent; wherein the total amount of slip agent in the film structure is sufficient for high speed heat seal packaging operations. a heat-sealable multilayer film structure; effective to provide a coefficient of friction to the outer surface of the outer layer (A), but in an amount insufficient to cause substantial hazing of the structure; 2. The film of claim 1, wherein the heat sealable resin is a terpolymer of propylene, ethylene and 1-butene. 3. The terpolymer is approximately 80-97% by weight propylene, approximately 1-10% ethylene, and approximately 1-20% by weight.
3. A film according to claim 2, comprising % by weight of 1-butene. 4. The film of claim 3, wherein the terpolymer consists of approximately 88-95% propylene, approximately 2-6% ethylene, and approximately 2-15% butene-1. 5. The film of claim 1, wherein the heat sealable resin is an ethylene-propylene copolymer containing approximately 1.5-10% by weight ethylene. 6. The film of claim 5, wherein the ethylene-propylene copolymer contains approximately 3-5% by weight ethylene. 7. The film of claim 1, wherein the heat-sealable resin is a propylene-butene-1 copolymer containing approximately 5 to 40 weight percent butene-1. 8. A film according to any of claims 1 to 7, wherein the heat-sealable layer (A) also contains approximately 5 to 15% by weight of microcrystalline wax. 9. A film according to any one of claims 1 to 8, wherein the heat-sealable layer (A) also contains approximately 0.05 to 0.3% by weight of glycerin monostearate. 10. The heat-sealable layer (A) contains antiblocking agent particles having an average particle size of approximately 0.5 to 5 microns.
The film according to any one of claims 1 to 9, containing 5% by weight. 11. A film according to any of claims 1 to 10, wherein the amount of slip agent in polymer composition (b) is less than the amount of slip agent in polymer composition (a). 12. The film according to any one of claims 1 to 11, wherein the slip agent in compositions (a) and (b) is erucamide. 13. Composition (a) is substantially 1000 to 2000 pp
m of erucamide, and composition (b) contains substantially 4 m of erucamide.
13. A film according to any one of claims 1 to 12, containing 00 to 800 ppm erucamide. 14. The polymer composition (C) further has approximately 0.5 to 5
Antiblocking agent particles having an average particle size of approximately 0.0 micron.
14. The film according to claim 1, wherein the film contains 0.05 to 0.5% by weight. 15. Claim 10, wherein the antiblocking agent particles are silica particles.
or the film described in 14. 16. The film according to any one of claims 1 to 15, wherein the outer surface of the outer layer (A) exhibits a coefficient of friction of 0.45 or less at room temperature. 17. The film according to any one of claims 1 to 16, wherein the outer surface of the outer layer (A) exhibits a coefficient of friction of 0.35 or less at room temperature. 18. The outer surface of the outer layer (C) has at least approximately 36 dynes/
18. A film according to any one of claims 1 to 17, having a surface activity of cm (36 mN/m). 19. The heat-sealable resin is a terpolymer of propylene, ethylene and 1-butene containing approximately 88-95% by weight of propylene and approximately 2-6% by weight of ethylene; the heat-sealable layer (A) further comprises approximately 5-15% by weight
of microcrystalline wax and approximately 0.05-0.3% by weight glycerin monostearate; polymer compositions (a) and (C) have an average particle size of approximately 0.5-5 microns. containing antiblocking silica particles; polymer composition (a) containing approximately 1000-2000 ppm erucamide; composition (b) containing approximately 400-800 ppm erucamide;
2. The film of claim 1, containing m erucamide. 20. The film according to claim 19, wherein the outer surface of the outer layer (C) exhibits a coefficient of friction of 0.3 or less at room temperature. 21. The film according to any one of claims 1 to 20, further comprising a coating of water-based adhesive adjacent to the outer surface of the outer layer (C). 22. The film of claim 21, wherein the water-based adhesive is selected from acrylic resins, urethane resins and vinylidene chloride polymers. 23. The water-based adhesive is a vinylidene chloride copolymer.
The film according to claim 21. 24. The film of claim 23, wherein the adhesive strength between the aqueous adhesive coating and the outer layer (C) is approximately 80 to 150 g/in.