JPH01500103A - sealable film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] sealable film The present invention is a film that is mainly made of polypropylene and that can be sealed by applying heat. related.

Various polypropylene films are disclosed, for example in British Patent No. 2028168A, European Patent No. Patent No. 002606, No. 135178 and German Patent No. 3.247,988 No. 1, in which the core or substrate of the film is polypropylene. be. Various additives, e.g. some modulus improvers, some antistatics Media, siloxanes and pigments can be added.

, However, none of these documents are based on conventionally known polyolefin films. It is possible to obtain a film with greatly improved sealing strength compared to We do not teach previously known fibres, which have only one type of component in the sealing layer. A seal that requires only one type of ingredient, with improved seal strength properties than A film with a sealing layer, i.e. whether the sealing strength is better at the same sealing temperature; Alternatively, we devised a film that can achieve the same sealing strength at a lower temperature. .

According to the invention, the sealable film includes a base layer comprising a polyolefin; The layer has on at least one of its surfaces 1 to 20% by weight, based on the weight of the base layer. The film layer has a weight of (a) 70 to 95, preferably 70 to 90. % linear low density polyethylene or at least one olefinically unsaturated monomer (at least one of the monomers has a functional group); 5 to 30, preferably 10 to 30% by weight of the linear low density polyethylene Tal or or a mixture with a resin having a molecular weight smaller than that of the polymer18). Ru.

These films can be used in the packaging industry and meet the requirements for such films. strict criteria such as sufficiently high modulus, inherent good transparency and properties. It can satisfy excellent sealing strength characteristics.

The base layer comprises a polyolefin, preferably 2 to 8 per molecule. Preferably, it is a polymer of mono-α-olefin containing 2 to 4 carbon atoms. is preferred, therefore this polymer contains the following olefins: ethylene, A homopolymer of pyrene, butene-1 and 4-methylpentene-1 or It can be a copolymer of two or more of these monomers. Particularly popular for the base layer of the film. The material used is polypropylene, especially propylene with high molecular weight and stereoregularity. It is a crystalline polymer. Also, propylene and other olefins up to 20 times , for example copolymers with ethylene, can also be used. Particularly preferred polyolefins are Density 0.86-0.92 g/cc measured according to ASTM D 1505 and ASTM DM 123B (230°C, 2.16 kg). An isotactic with a melt flow index of 1” 15 g/10 min measured as It is polypropylene. This includes, for example, AmICJ, and TiCj! a It can be obtained by the Ziegler polymerization method using as a catalyst.

The base layer or core of the film has said base layer on one or preferably both of its surfaces. 1-20% by weight, preferably 1-10% by weight for each surface, based on the weight of the main layer , particularly having a film layer of about 5% by weight, said film layer having (a) 70-95, preferably or 70-90% by weight of linear low density polyethylene or polymers as defined above. and (b15-30, preferably 10-30% by weight of a low molecular weight resin, preferably Contains mixtures with hydrogenated resins.

The linear low molecular weight polyethylene (LLDPE) is manufactured according to ASTM D 1505. with a density of 0.875 to 0.939 g/cc, and at least 85 Ethylene and alpha-olefins, such as butene, hexene, containing mol% ethylene or defined as a linear copolymer with octene or 4-methyl-pentene-1. be justified. This is typically done with Ziegler catalysts such as ^JCjl and TiC1a. prepared by polymerization in the presence of

One particular example of linear low density polyethylene is very low density polyethylene. nsity) polyethylene, VLDPE. This is ASTM 01505 It has a density of 0.875 to 0.915 g/cc measured according to Containing 85-96 mol% of ethylene and α-olefins such as butene, hexene or or a linear copolymer with octene or 4-methyl-pentene-1. child Both are usually prepared by polymerization in the presence of a Ziegler catalyst.

At least one type of olefin may be used instead of linear low-density polyethylene. Finically unsaturated monomers (however, at least one of the monomers has a functional group) ). A functional group is a group other than a carbon or hydrogen atom. Also groups containing one type of atom, such as hydroxyl, carboxyl, carboxyl anhydride carboxylate, ester, amino, amide, imide, halogen or carbon shall mean a sulfonate group.

Suitable examples are ethylene-vinyl acetate copolymers, polyvinyl chloride, polychlorinated Vinylidene, styrene-acrylonitrile copolymer and acrylonitrile- Example 0 polymer, which is a butadiene-styrene copolymer, has one of the monomers Free of tyrene or acrylic acid, methacrylic acid, acrylate esters, maleic acid Random and graphical monomers such as polar monomers, including hydrates and other anhydrides. Futocopolymers and ionomers formed by adding metal salts to such copolymers - Including materials.

Generally, unsaturated monomers copolymerizable with ethylene include unsaturated acids, acid anhydrides, and the following. including diesters of the general formula: where R2 is hydrogen or methyl; 00CR4 or C0OR.

(Here, R4 is hydrogen or a straight chain group having 2 to 3 carbon atoms, preferably 1 to 4 carbon atoms, or represents a branched alkyl group), and R3 is hydrogen or -COOR4. this When R1-R3 are hydrogen and when R2 is -COOR, the monomer is , vinyl alcohol esters of monocarboxylic acids having 2 to 17 carbon atoms. child Examples of esters such as vinyl acetate, vinyl isobutyrate, vinyl lau including vinyl myristate, vinyl palmitate, etc. R2 is -COO R.

, such esters are C, oxyT alcohol acrylate, Acrylate, methyl methacrylate, lauryl acrylate, inbutyl methacrylate rylate, palmityl alcohol ester of α-methacrylic acid, Contains C+a oxo alcohol ester, etc. R1 is hydrogen, and R2 and An example of a monomer in which R and R is -RorocR1 is C+soxolecorcol fumale. -C+S-oxoalcohol fumarate, di-isopropyl maleate, di- - Lauryl fumarate, ethyl methyl fumarate, fumaric acid, maleic acid, etc. including.

Other unsaturated monomers copolymerizable with ethylene include propylene, n-octene, etc. -Cs=C+s branched or direct, such as -1,2-ethyldecene-1%n-decene-1 Contains anti-α-monoolefin.

A small amount, for example about 0 to 20 mol %, of a third monomer or even a fourth monomer These can be included in the above copolymers, such as propylene, n-octyl Ct-C+ a-branched or linear monoolefins such as ten-1 and n-decene-1 It is. Thus, for example, 3 to 40 moles of ethylene and 30 to 99 mole percent unsaturation. ester and 1 mole of a mixture of 70-1 mole % olefins. Can be used.

The copolymer formed is primarily composed of an ethylene polymer backbone and distributed along it. A random copolymer consisting of hydrocarbon or oxy-substituted hydrocarbon side chains. be.

The oxoalco-J used in preparing the above esters is prepared from olefins. isomeric mixtures of branched-chain aliphatic alcohols, such as C1-C4 monooleic fin polymers and copolymers, which are treated with cobalt-containing catalysts, e.g. In the presence of baltocarbonyl at a temperature of about 300-400"F, about t,ooo to 3 ．． Under a pressure of 000 psi, - is reacted with carbon oxide and hydrogen to form a! Ledehi It is said to be The resulting aldehyde product is then hydrogenated to produce the oxoalcohol. The latter is recovered from the hydrogenated product by distillation.

Particular examples include ethylene and C, ~C,. Monocarboxylic acid vinyl (or hydro copolymers with carbyl-substituted) vinyl esters, preferably at least 89 wt. % of ethylene (e.g. ethylene-vinyl acetate copolymer) - ethylene-vinyl acetate, including cixo% by weight of vinyl acetate Copolymer, ethylene-vinyl acetate copolymer containing 95% by weight ethylene -, or 0.10 to 1.95% vinyl (or - hydrocarbyl) (vinyl acetate).

Other components of the surface layer are low molecular weight resins, preferably hydrogenated resins.

This resin has a lower molecular weight than the polyethylene or polymers mentioned above and is usually s,ooo or less, preferably 1,000 or less, for example 500 to 1,00 It is 0. This resin may be a natural or synthetic resin and may be between 60 and 180°C, e.g. according to ASTM E-28, preferably 80-150°C, preferably 80-140°C. It can have a softening point measured as follows.

Suitable resins that can be subsequently hydrogenated include hydrocarbon resins, ketone resins, polyamide resins, copolymer resins, etc. Lojou, coumaron resin, terpene resin, chlorinated aliphatic or aromatic hydrocarbon tree It's fat. Examples of hydrocarbon resins are coke oven gas, cracked naphtha, gas oil and telco. It is a polymer of pen oil.

Particularly preferred hydrogenated resins are hydrogenated petroleum resins. These are usually thermally polymerized steam A thermal polymerization of a cracked petroleum distillation fraction, especially a fraction with a boiling point in the range of 20 to 280°C, is used. It is prepared by catalytic hydrogenation. These two parts are usually one or more in the molecule. Compounds with the above unsaturated rings, such as cyclodienes, cycloalkenes and It is an indene. In addition, the resin produced by catalytic polymerization of unsaturated hydrocarbons is It is also possible to attach it.

Before hydrogenation, the polymerized resin is dissolved in a saturated hydrocarbon solvent, e.g. heptane. It is normal. The hydrogenation catalyst used is nickel, reduced nickel or molyb sulfide. It could be Den. Hydrogenation at 200-330°C, preferably 210-230°C , in one step for 5 to 7 hours under 20 to 120 atmospheres, preferably 30 to 90 atmospheres. I can. After filtering off the catalyst, the solvent is distilled off and recycled for recycling. collect. An improved hydrogenation process that provides high yields of high-grade hydrogenated hydrocarbon resins has been awarded a European patent. No. 0082726 (application number 82306853.1) and Permission has been requested.

Each outer film layer consists of 75-84.5% by weight linear low density polyethylene or is a polymer as defined above and 15.5 to 25% by weight of a low molecular weight resin, e.g. Contains by weight % polyethylene or polymer and about 20% by weight low molecular weight resin It is preferable.

The film of the present invention, i.e., the multilayer film, includes the components of the base layer and the surface layer (if necessary). For example, it may contain other ingredients such as antistatic media, blocking agents and slip aids. ) can be combined by known methods, preferably coextrusion. more advantageously formed.

The multilayer film according to the present invention may be unstretched or uniaxially stretched, but is preferably Alternatively, the film is axially stretched by pulling it in two mutually perpendicular directions within the plane of the film, and then give degree. Stretching of flat films can be carried out by the tenter method; The resulting tubular film is produced by simultaneously stretching polymeric material in the form of a multilayer tube from an annular guide. Then, this extruded tube (formed tube) is cooled, and the iron tube is made into a so-called "bubble". reheating and expansion by ``ble method'' to give transverse stretching and at the same time Advantageously obtained by stretching the tube in the longitudinal direction and stretching the film in the longitudinal direction. It will be done. Preferably, the film is then "heat set". That is, The dimensional stability of the film is improved by heating the film, while resisting heat shrinkage. is suppressed north. The heating is carried out at the glass transition temperature of the polymer (above this point a film is formed). ) and below its melting point.

The thickness of these films can vary depending on the intended use, but is typically 2. A film thickness of ~150μ is suitable. Packaging film is usually 1O~60μ The thickness is . The thickness of each layer (example film layer is usually 0.05-2.5μ).

1 group In this example, we produced coextruded films with different compositions and compared their sealing suitability. Ta.

These films can be pulled in two substantially orthogonal directions in the plane of the cough film. The film was then biaxially stretched to impart strength. Stretching ratio in machine direction using tenter method 500% and a stretching ratio of 900% in the transverse direction. Each biaxially stretched film is It had two sealing layers 1μ thick, while the total thickness was about 22μ.

The first film as a comparative example had a core of isotactic polypropylene. , the polypropylene has a density of about 0.05 as measured by ASTM D 1505.　9　 0g/cc and ASTM D 1238 (230℃, 2.16kg It has a melt flow index of 2.8 g/10 minutes measured according to the following conditions: It was. Approximately 95.5% by weight propylene and 4.5% by weight are deposited on both sides of the core. It has a layer of copolymer with ethylene, the copolymer having a density of 0. 9 0 g/ cc and ASTM D 1238 (230℃, 2,16kg conditions) It had a melt flow index of 6.5 g/10 min, measured according to the method.

The second film is the same as the first film but is made of isotactic polypropylene. LLD differs in that it has LLDPE films on both sides of the core. PE is produced by copolymerizing ethylene and n-butene using a Ziegler catalyst. This is linear low-density polyethylene prepared by This copolymer has at least 96 It contains mol% ethylene and a density of 0.918 g/cc.

The third film is the same as the first film above, but each surface of the core is 80 wt. % LLDPE (see second film for details) and 20% by weight hydrogenated petroleum resin. The thermal polymerization of distillate fractions is coated with a film containing a blend of It was prepared from The hydrogenation method is patented in European Patent No. 0082726 (application number 823068). 53.1). The obtained resin is AST? I　E　2B It was characterized by a ring and ball softening point of 125°C, measured according to the method.

The fourth film was the same as the third but with 80% by weight on each surface of the core. of VLDPE and 20% by weight of the same hydrogenation used in the synthesis of the second film. It differs in that it is coated with a film containing a blend with petroleum resin. VLDPE is prepared by copolymerizing ethylene and octene using a Ziegler catalyst. The copolymer contains 95 mol% ethylene. and a density of 0.911 g/cc measured according to ASTM D 1505. and according to ASTM D 1238 (190°C, 2.16 kg conditions) The measured melt flow index was 7.0 g/10 minutes.

Attached Figures 1 and 2 show films 1 and 2 (comparative examples) and 3 and 4 (comparative examples). This figure shows the measurement results of sealing strength and thermal adhesion obtained for the present invention).

These tests were conducted as follows.

Sealing strength This is the “cold” heat seal strength of the film; Measured after the seal has cooled to ambient temperature and the seal has developed sufficient potential strength. be done.

Design & Test Consultation (Design & Test Consultation) Te5t Con5ult) A B C Bromma Sweden Pack tester (Pack) from -Si1eden) forsk Hot Tack Te5ter) 0 width 1 using model 52-B A strip of approximately 2,801 mm long is folded back and placed between the heated jaws of the device. sealed together. The seal formed has an area of approximately 15×5ts. This seal The holding pressure conditions at the top were kept constant at a pressure of 5 bar and a residence time of 0.5 seconds.

To measure the sealing strength, measure the hot tack when opening the sealing jaws. The device is used in such a mode that the automatic stripping action used to perform the procedure is inoperable.

Instead, the seal is cooled to ambient temperature and then the remaining portion of the strip is cooled to ambient temperature. Attach the sealed end to the jaws of the tensile tester.

The tester records the force required to break the seal at a rate of 508 dragons per minute. , the sealing strength is expressed in units of kg/i5m.

Silk plate koji rich harvest This occurs immediately after sealing and the thermal energy used to form the heat seal is dissipated. This is the strength of the heat seal measured before.

This hot tack was measured using the same PACL (forsk) equipment. went. Heat sealing is performed as described above, and the peeling action occurs immediately after opening the sealing jaw. automatically starts, automatically records the force required to break the seal, and The adhesiveness is expressed in units of kg/15m. This stripping operation is performed with a controlled delay time (the time between the opening of the jaw and the start of the peeling operation) and controlled. Perform the peeling process at a peeling speed that is as follows. For all hot tack measurements, certain conditions such as: was used. That is, delay time - 0.9 seconds; peeling speed = 100 m/s From the results shown in Figure 1, the sealing strength Ckt/15w) for films 3 and 4 is 1 Higher than films 1 and 2 at temperatures ranging from 00 to 120 °C I can understand.

From Figure 2, the hot tackiness (kg/15 am) of film 3 is up to about 130°C. It can be seen that the temperature is much higher than that of film 1. to film 4 Therefore, hot tack is better than film l for temperatures up to about 110'C. It is.

The presence of a relatively small amount (20% by weight) of hydrogenated resin in the surface layer and the linear low Due to the use of density polyethylene, such good results compared to conventional films It is quite surprising that this can be obtained.

Sealing temperature (0C) Yoshi, Commissioner of the Patent Office 1) Takeshi Moon 1. Incident indication PCT/GB8710 O3752, title of invention Sealable plastic ;Film 3, corrector Relationship to the case: Applicant 5. Date of amendment order: Self-issued rw inspection report

Claims (1)

[Claims] 1. a base layer comprising a polyolefin, the base layer being on at least one surface thereof; has a film layer of 1 to 20% by weight based on the weight of the base layer, the film layer having ( a) 70-95% by weight of linear low density polyethylene or at least one olefin phosphorus-based unsaturated monomers, provided that at least one of the monomers has a functional group; a polymer; and (b) 5 to 30% by weight of the linear low density polyethylene or the polymer. A sealable film characterized by comprising a mixture with a resin having a molecular weight smaller than that of Lum. 2. The film layer is specified in claim 1 in an amount of 70 to 90% by weight. and 10 to 30% by weight of the above resin. The film described in section. 3. The polyolefin in the base layer is mono-containing 2 to 4 carbon atoms per molecule. Claim 1: Polymer of α-olefin, preferably polypropylene Or the film according to item 2. 4. The density of the above polypropylene measured according to ASTM D1505 is 0.86~ 0.92g/cc and ASTM D1238 (230℃, 2.16kg conditions) ) with a melt flow index of 1 to 15 g/100 min measured according to 4. The film according to claim 3, which is an isotactic polypropylene. 5. The base layer has on each surface thereof 1 to 10% by weight, based on the weight of the base layer. a film layer, said film layer being made of linear low density polyethylene or polyethylene as defined above. as claimed in any one of the preceding claims, comprising a mixture of reamer and low molecular weight resin. film. 6. The above claim wherein the resin in each of the film layers is a hydrogenated resin, preferably a petroleum resin. The film according to any one of the following ranges. 7. The resin has a softening point of 80 to 140°C as described in ASTM E-28. A film according to any one of the claims. 8. The above hydrogenated resin is thermally polymerized at a temperature of 200 to 330°C using a hydrogenation catalyst. prepared by hydrogenation of steam cracked distillation fractions or catalytically polymerized unsaturated hydrocarbon fractions. Any one of claims 5 to 7, characterized in that The film included. 9. The linear low density polyethylene has a density of 0 as measured by ASTM D1505. ．． 875 to 0.939 g/cc and at least 85 mol% ethylene. The claimed invention is a linear copolymer of ethylene and α-olefin comprising The film according to any one of the above. 10. The above α-olefin is butene, hexene, octene or 4-methyl pen The film according to claim 9, which is Chin-1. 11. The copolymer has a density of 0.875 to 0.915 g/cc, and The film according to claim 9 or 10, containing 5 to 96 mol% ethylene. Mu. 12. The polymer of at least one olefinically unsaturated monomer described above is and vinyl or (hydrocarbyl-substituted) vinyl of C1-C30 monocarboxylic acids. According to any one of claims 1 to 8, which is a copolymer with a nyl ester. The film mentioned. 13. Each of the above surface film layers has a linear low density polyethylene content of 75 to 84.5% by weight. or a polymer comprising a polymer as defined above and 15.5 to 25% by weight of a low molecular weight resin. A film according to any one of the claims. 14. Any of the above claims characterized in that the film is biaxially stretched. The film according to item 1 above. 15. The film has a thickness of 10 to 60μ, and each outer film layer has a thickness of 0 ．． 05 to 2.5μ.