JPH0237941B2 - - Google Patents

Description

[Detailed description of the invention]

Heat-sealing compositions that exhibit a sufficiently wide heat-sealing temperature range to reproducibly produce permanent and peelable seals in the same package with different film materials in the production of flexible film packages by heat-sealing processes. The demand for this has been going on for a long time. The permanent seal in such a package is preferably strong enough that seal failure occurs by tearing the packaging film, and the peelable seal is strong enough to retain the contents of the package. is preferably sufficiently weak to allow separation of the package walls by moderate force. The rupture of the peelable seal is preferably a cohesine failure of the heat seal composition itself, and the failure is clean and free of loose debris of the heat seal composition. It is preferable that there be. It is important that the temperature range between forming the peelable seal and the permanent seal is wide. This is because, for wide temperature ranges, a single heat-sealing device can be used to create peelable and permanent seals without the need to incorporate highly sensitive temperature control devices into the heat-sealing device. Because it can be done. U.S. Patent No. issued February 12, 1980
No. 4,188,441 discloses blends of high density polyethylene films and useful polymers to form peelable heat seals. The blends in the above patents are disclosed to be ethylene vinyl acetate or acrylic ester binary copolymers and sodium neutralized ionomers. The disclosed objective is to create only peelable seals; permanent seals are avoided as undesirable. Regarding McDonald's application
U.S. Patent No. 3707393 issued December 26, 1972
No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, 2003, 2003, discloses heat sealing applications of combinations of ionomers and, in certain instances, terpolymers. A combination of materials is simply a physical mixture;
It is not a blend with partial neutralization of both polymers. January 1974 for the application of Iwami et al.
US Pat.
Discloses a method that can neutralize by contact). The patent also discloses the separation of the polymer so neutralized. For applications such as Freshhour, etc.
U.S. Patent No. 3496061 issued February 17, 1970
No. 5,193,901 discloses a heat-sealed package manufactured using at least two different materials such that at least one seal exhibits a peel strength greater than 400 g/in. U.S. Pat. No. 4,189,519, issued February 19, 1980 to Ticknor, discloses a blend of polymeric materials that act as a heat seal composition in which one necessary compound is isotactic polybutylene. Disclose. The present invention encompasses heat sealing compositions that exhibit a wide effective temperature range for achieving controlled strength heat sealing to a variety of substrate materials. The composition comprises about 20-80 parts by weight of the terpolymer and 20-80 parts by weight of the terpolymer.
A partially neutralized ionomer and terpolymer blend containing parts by weight of ionomer.
Both polymers contain unsaturated monocarboxylic acids as monomer components. Total carboxylic acids in the blend range from 5 to
40% neutralized. The heat seal compositions of the present invention exhibit a wide temperature range for forming heat seals of varying strengths. The compositions of this invention enable the production of film, foil or paper packages with permanent side or bottom seals and peelable top seals. Heat seal compositions have long been used to form packages from films, foils and papers.
The packaging material support is typically coated on one side with a heat-sealing composition, the coated sides are then brought together face-to-face, and the joined material is heated in the intended seam area to melt the heat-sealing composition and Creates package seams. According to the present invention, ethylene as a monomer component,
terpolymers with vinyl alkanoates or unsaturated alkyl esters and partially neutralized unsaturated carboxylic acids, and ionomers with ethylene and partially neutralized unsaturated carboxylic acids as monomer components. A substantially homogeneous blend of polymeric materials is provided as a heat seal composition. The terpolymer has about 65-95% by weight ethylene, about 4-30% by weight vinyl alkanoate or unsaturated alkyl ester, and about 0.5-20% by weight unsaturated carboxylic acid. The vinyl alkanoate or unsaturated alkyl ester monomer component is present in the terpolymer to provide a component for increased adhesion to film, foil and paper supports and also to provide increased flexibility to the composition. properties and widens the effective heat-sealing temperature range. Unsaturated alkyl esters include alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 4 carbon atoms. Examples include methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl acrylate, and the like. Vinyl alkanoates include vinyl acetate, vinyl propionate, vinyl butyrate, etc. in which the alkanoic acid moiety of the vinyl alkanoate has 1 to 4 carbon atoms. For paper and foil supports 10-30% by weight of vinyl acetate is preferred;
For polymeric film supports, 5 to 25% by weight of isobutyl acrylate is preferred. Terpolymers with too little of a vinyl alkanoate or unsaturated ester component generally exhibit poor adhesion and a narrow heat-sealing temperature range, whereas an excess of that component reduces the tackiness of the heat-sealing composition. become excessive. Terpolymers can have more than three monomer components so long as the additional components do not interfere with the function of these three components necessary to practice the invention. A carboxylic acid monomer component is present in the terpolymer to provide a component similar to the acid component in the ionomer. It is believed that the presence of the carboxylic acid component in each of the blend polymers provides cooperation between the polymers. Although the mechanism is not completely understood, the presence of the carboxylic acid component in each of the blended polymers primarily increases the temperature range over which a peelable heat seal can be formed.
Second, it creates a degree of compatibility between the polymers, evidenced by a substantial increase in the maximum heat seal strength that can be obtained with blends of similar materials without a common carboxylic acid component. it is conceivable that. Preferred carboxylic acids include acrylic acid and methacrylic acid. These components can be used in amounts of 0.5 to 20% by weight of the terpolymer components, and 0.8 to 15% by weight of either acid is preferred. At too low acid contents, the above-mentioned compatibilizing effect is lost, and at too high acid contents, the terpolymer exhibits an undesirably high modulus. Terpolymers containing carboxylic acid components and suitable for use in the practice of this invention are described in US Pat. No. 3,264,272. The ionomer has about 75-99% by weight ethylene and about 1-25% by weight unsaturated carboxylic acid. For use in the present invention, the ionomer should preferably have from 3 to 20% by weight of unsaturated carboxylic acid. About 5% to about 75% of the carboxylic acid groups in the ionomer should be neutralized by zinc metal ions. Ionomers suitable for use in the practice of this invention are described in US Pat. No. 3,355,319. As mentioned, the combination of acrylic or methacrylic acid in the terpolymer and acrylic or methacrylic acid and vinyl alkanoate or alkyl acrylate or methacrylate in the ionomer provides improved adhesion, improved polymer compatibility and Balances the expanded heat sealing temperature range. In order to obtain a sufficient profit,
The combined weight percentage of the acrylic acid or methacrylic acid component and the vinyl alkanoate or unsaturated alkyl ester is at least eight percentage points greater than the weight percentage of the unsaturated acid in the ionomer.
It has been found necessary to provide large terpolymer materials. Since these benefits are mostly related to softening or modifying the melt temperature of the blend, component ratio requirements are used within the overall requirement that no less than 20% and no more than 80% by weight of each material must be present in the blend. The amounts of terpolymer and ionomer are believed to be virtually independent. The various components of the heat seal composition are combined to form a molecular mixture of materials. The combination can be accomplished by any conventional method of blending materials. For example, solutions of the materials can be mixed and the solvent subsequently removed, the materials can be mixed together in molten form such as by melt blending in an extruder, or the materials can be mixed together, e.g. They can be mixed together in a two-roll mill or in a Banbury blender. The primary requirement for blending is that the resulting blend must be substantially homogeneous and that the blending be sufficiently intimate to allow equalizing neutralization between the carboxylic acid groups of the terpolymer and ionomer. This means that a certain material mixture must be produced. Extrusion blending has been found to be suitable and preferred for producing the blends of the invention. In the blend, the terpolymer contains partially neutralized carboxylic acid groups;
It is therefore understood that terpolymers can be identified as ionomers. In fact, the blends of the present invention can also be prepared from two ionomers or from a three-component ionomer and an unneutralized copolymer or, if desired, from a suitable combination of such components. Additionally, the blend can be made by melt blending unneutralized copolymers and terpolymers and then neutralizing the blended mixture. Suitable methods for carrying out such neutralization are disclosed in US Pat. Nos. 3,404,134 and 3,969,434. As far as carboxylic acid groups are concerned, it is only necessary that the finished blend must contain the carboxylic acid groups in each polymer component neutralized to the required degree. It has been found that the benefits of the present invention are found when the degree of neutralization of all carboxylic acid groups in the blend is between 5% and 40%. Terpolymer and ionomer materials require the total neutralization obtained if the degree of neutralization of the unblended, neutralized material is averaged with the unneutralized material between the blending groups. selected to be within the range. The heat-sealing compositions of the present invention can be used in the manner in which heat-sealing compositions are commonly used. It is a self-supporting structure, for example in the form of a sheet, strip or web.
structure). It can be coated onto the support packaging material as a solution or emulsion, it can be coextruded with the support packaging film material, and it can be laminated to the support material using an adhesive. The heat seal compositions of the present invention can be used with a variety of carrier packaging materials. As mentioned above, the monomer components of the terpolymer and ionomer can be specifically selected to specifically increase the adhesion of the heat seal composition to the support packaging material. Furthermore, if high density polyethylene, polypropylene, polyester, polyamide, etc. are to be used as the support packaging material, metal ions with a valence greater than 1 may be added to neutralize the carboxylic acid groups of the heat seal composition. It was found that it is important to use Zinc is the preferred metal ion and is most commonly used in such cases. Zinc has been found to provide the required wide heat sealing temperature range. In forming a peelable heat seal to a flexible package, it is usually desirable and often necessary for seal rupture to occur within the heat seal composition. It is therefore important that the heat seal composition layer should adhere more strongly to the support material than to itself when the peelable heat seal is formed. If a permanent or fused heat seal is to be formed, the heat seal compositions should be fused together and bonded to the support material so strongly that tearing of the support material will occur before rupture of the heat seal. It is desirable that the seal should be bonded and that, in any event, the seal not fail due to separation of the fused heat seal composition. The use of zinc as the neutralizing metal ion and the use of suitable vinyl alkanoates or unsaturated esters in the terpolymer, especially vinyl acetate or isobutyl acrylate, are important in obtaining maximum fusion heat seal strength for various support packaging materials. It is thought that. One important feature of the heat seal compositions of the present invention is that the temperatures required to achieve a low strength peelable heat seal allow the heat seal compositions from the combined materials to completely fuse together. A wide heat sealing temperature range extending to that temperature required for maximum strength permanent heat sealing. The wide temperature range for heat seals formed using the heat seal compositions of the present invention provides a self-supporting film of the heat seal composition.
orted films) and then forming a series of heat seals on these films at a range of temperatures. The heat seal so formed was tested for peel strength and
Peel strength and tear seal of 118g/cm (300g/in), 275g/cm (700g/in)
Record the temperature that occurs. Tear seal indicates the maximum seal that can be obtained for a given support material. This is because the seal strength actually represents the tear strength of the support material or the cohesine strength of the fused heat seal composition. When performing peel strength tests using films of heat seal compositions, tear sealing occurs at a temperature where the composition is sufficiently melted.
In determining the temperature at which the heat seal is made, it is important to determine the temperature of the interface between the heat seal composition layers rather than the heat seal jaw or bar temperature. Calibration errors or heat transfer variations in the heat sealing equipment can cause the seal jaw temperature to be higher or lower than the actual interface temperature by an unpredictable amount. For purposes of the present invention, it has been determined that a temperature range of at least 7°C, preferably greater than 8°C, is acceptable for the peel seal zone (118-275 g/cm). It has been found desirable, if not necessary, to have a temperature range of at least 8° C., preferably greater than 10° C., for the tear seal zone (275 g/cm to tear). fillers, dyes, antioxidants, non-stick agents,
Conventional additives such as antistick agents and the like can be added to the heat seal compositions of the present invention.
The only requirement here is that the presence of the additive does not adversely affect the performance of the composition. Slip agents such as silica and substituted fatty amides are examples of additives that can be added in conventional amounts. Additives are conveniently and conventionally added to heat seal compositions during blending and are usually not present in amounts exceeding 5% by weight of the total composition. In the following inventive examples, the component materials of the heat-sealing compositions were prepared by first mixing the materials in particulate form in the amounts shown in the table below, then melt blending, and making a 28 mm Werner & Werner & Pfleiderer twin-screw extruder
The mixtures were blended together by devolatilizing the mixture in an extruder such as the following. The extruded blend is made into pellets and the pellets are processed to produce test films.
Convert to blow molded film in a 1.9 cm (0.75 inch) Brabender extruder with a 2.5 cm (1.0 inch) die. The film is typically 0.05 mm (2 mm) thick with a blow-up ratio of 2.5;
It was then cast at a melting temperature of 190-210°C. The film is cut into 2.5 cm (1 inch) wide pieces for testing, and the sample pairs are heat sealed together to give a 2.5 cm (1 inch) peel length. The seal is made with two heated jaws having a width of 2.5 cm (1 inch), and the heat seal is approximately
A clamping pressure of 275 k Pascals (40 psi) was applied for approximately 3 seconds. Interfacial seal temperatures were determined by placing thermocouples between the film samples being sealed and then calibrating the sealing device against these samples. Peel strength was determined by pulling the sealed samples at 23°C and 50% relative humidity in a tensile testing apparatus at a speed of 12.7 cm/min (5 in/min). Peel strength was evaluated as a function of interfacial seal temperature, and peel and tear seal zones were determined therefrom. These decisions are recorded in the table below.

【table】

【table】

【table】

【table】

【table】

TABLES In the Examples and Tables, the polymeric component materials are identified as follows. E/10IBA/10MMA is ethylene and 10% by weight isobutyl acrylate and
Terpolymer with 10% by weight methacrylic acid, E/28VA/1MAA is ethylene and 28% by weight
of vinyl acetate and 1% by weight of methacrylic acid, and E/XMMA is a copolymer of ethylene and 1% by weight of methacrylic acid as indicated by the number substituted for "X" in the table. be. In the examples of the invention described below, the blends from the previous examples were coextruded with high density polyethylene as a support packaging material, with one film of the blend adhered to the support packaging material as a heat seal composition. A flexible packaging material of high density polyethylene film is obtained. The coated polyethylene was then tested for heat seal strength as the films of the blend were previously tested. Such a packaging material of a blend coated on a support material is prepared by placing two sheets of coated material with a heat seal layer facing each other and then using a controlled temperature heat sealing machine. It is used to manufacture packages by forming heat seals, possibly with varying or desired strengths.

【table】

Claims (1)

[Scope of Claims] 1a Monomer components: 65-95% by weight of ethylene, vinyl alkanoate in which the alkanoic acid moiety has 1 to 4 carbon atoms, or vinyl alkanoate in which the alkanoic acid moiety has 1 to 4 carbon atoms; and an ethylenically unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid.
20-80% by weight of a terpolymer having 0.5-20% by weight; b. 75-99% by weight of ethylene and an ethylenically unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid 1 as monomer components; 20 to 80% by weight of an ionomer having an ionomer of up to 25% by weight, and the sum of the weight percentages of the comonomer in the terpolymer is at least 8% higher than the weight percentage of the comonomer in the ionomer; and a substantially homogeneous blend of polymeric materials in which 5 to 40% of the carboxylic acids in the blend are neutralized by zinc ions. 2. The blend of claim 1, wherein the monomer of the terpolymer is a vinyl alkanoate, and the vinyl alkanoate is vinyl acetate. 3. The blend of claim 1, wherein the monomer of the terpolymer is an alkyl acrylate and the alkyl group is isobutyl. 4. The blend of claim 1, wherein the self-supporting film of the blend material exhibits a peel seal (118-275 g/cm) temperature range of at least 7°C. 5. The self-supporting film of the blended material has a tear seal of at least 8°C (275 g/tear).
cm) Blend according to claim 4 indicating the temperature range.