JP2011153322A - Radiation-cured, laminated flexible packaging material and radiation-curable, adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated flexible packaging material (20) suitable for containing a pharmaceutical, food or beverage grade product. <P>SOLUTION: The laminated flexible packaging material includes a layer (26) of flexible packaging material bound to at least one other layer (22) of flexible packaging material by a radiation-cured laminating adhesive composition (24). The radiation-curable laminating adhesive (24) is prepared with the radiation-curable, adhesive composition including: at least 50% by weight of one or more radiation cured carboxylic acid functional monomer and 0.1 to 20% by weight of an organic zirconate or the like. There is also provided a radiation-curable laminating adhesive comprising: at least 50% by weight of one or more carboxylic acid functional monomers and 0.1 to 20% by weight of an organic zirconate compound or the like. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiation-cured laminated flexible packaging material. The present invention also relates to a radiation curable adhesive composition suitable for use in the formation of the laminated flexible packaging material.

  Flexible packaging is widely used for food, non-food, and pharmaceuticals. Flexible packaging uses a wide variety of different types of materials, including various types of plastic film, paper, and aluminum foil. The plastic film includes various types of polyolefins, polyesters, and polyamides. The film may be various combinations of homopolymers, copolymers, and polymer blends. The film may be a single layer or a coextruded multilayer. Also, in general, the film is coated, vapor deposited, or otherwise processed to enhance the performance of the resulting packaging material. The packaging material is selected based on a variety of factors including desired barrier properties, appearance, cost, lift, printability, sealability, ease of opening, and resealability.

  Two main classes of flexible packaging materials are: 1) mono-web packaging, including co-extruded film mono-web; and 2) laminated packaging. Often, laminated packaging is desirable due to the fact that it is convenient to join two or more webs to obtain the desired properties of the resulting packaging. The reasons for using the laminated packaging structure are: 1) to provide protection and good appearance, to add drawings between layers; 2) to take advantage of the barrier properties of individual layers to maintain product freshness; 3) To combine a heat stable web for printing and a heat-sealable web that seals the packaging; 4) provide desired feel and handleability to maximize consumer appeal 5) To increase the strength of the packaging in order to maintain the integrity of filling, delivery and consumer handling.

  Several different techniques are used to adhere the layers used in laminated packaging. There are two types of lamination techniques: extrusion lamination and adhesive lamination. Extrusion laminating involves melting and welding a layer of thermoplastic resin, such as polyethylene, between two webs of packaging material. In general, the different types of adhesives used in laminated flexible packaging materials are: 1) one component solvent base; 2) two component solvent base; 3) one component water base; 4) two component water base; Includes two-component solvent-free.

There are inherent limitations for solvent-based adhesives: 1) emission of volatile organic compounds (VOCs); 2) high cost of incineration of solvent or recovery equipment; 3) flammability; and 4) the Includes analysis and control of residual solvents in packaging materials. There are inherent limitations to water-based adhesives: 1) the need for long-term drying equipment; 2) the effect of heat used to dry heat sensitive packaging films; 3) drying depending on ambient humidity values Speed change; and 4) Since the adhesive is dried by the applicator, it includes difficulty in starting and finishing.
All binary systems (solvent-based, water-based, or solvent-free) have inherent disadvantages: 1) The need for accurate mixing of the two components; 2) Limiting the pot life of the mixed components And 3) including the time delay required for the reaction of the two components (generally 2-5 days) to achieve final adhesion. Other limitations associated with two-component solventless adhesives are: 1) the need to heat the applicator; and 2) residual toxic aromatic amines that are isocyanate by-products based on the curing system including.

  Potentially, radiation curable adhesives can provide many advantages over these other flexible packaging lamination adhesives. These can provide: 1) a stable fractional composition; 2) little or no VOCs; and 3) a fully cured adhesive capacity. UV curable laminating adhesives require at least one layer of packaging material that is sufficiently transparent to transmit UV light in order to cure the adhesive. EB curing to cure the adhesive has the additional advantage of being opaque or being able to penetrate the printed packaging.

  Important issues in the development of radiation curable bonding adhesives are: 1) provide adequate adhesion and chemical resistance for application of the desired packaging material; and 2) enable food and drug packaging. It has low odor, low contamination, and low migration. In general, radiation curable materials such as inks and paints are based on reactive monomers and oligomers that are relatively low molecular weight. The component is designed to be converted to a high molecular weight polymer upon UV or EB irradiation. A high conversion of the low molecular weight component can be achieved; however, usually some residual amount of monomer or oligomer remains. These remaining components cause odor, contamination and migration problems of the packaging material. The radiation curable ink and paint technology does not address the same problems associated with flexible laminate packaging, so that those skilled in the art will be able to address the problem with the radiation curable used in laminates. When addressing the problems with adhesives, there will be no motive to investigate the technology of the radiation curable ink and paint.

  A discussion of issues relating to the use of radiation curable materials in food packaging applications can be found in PCT application number WO02 / 081576 (Chatterjee), which is incorporated herein by reference. . According to Chattery, the disclosed compositions contain water and replace radiation curable inks or paints. This is not possible with a laminating adhesive as the water is trapped between the two layers of packaging material, so chattery is related to radiation curable adhesives used in laminate formation. It does not help in addressing the problem.

  In radiation curable laminating adhesives, initially the remaining low molecular weight component is found in the cured adhesive between the two layers of the packaging material. A type of packaging material, such as aluminum foil, is a good barrier and is effective in preventing migration of low molecular weight components into food or pharmaceutical products. Other packaging materials, such as polyolefin base materials, are known to have a low barrier effect against the migration of low molecular weight organic compounds. Accordingly, there is a need for a radiation curable adhesive material that, when properly cured, substantially reduces migration through the layer of laminated flexible packaging material.

  Also, especially when the packaging material contains highly reactive liquids or foods with some activity, flexible packaging materials have the problem of delamination of the layer during normal use. Delamination can also be a problem during processing or packaging. This can include closure, filling, sealing, and the addition of thermal processing. Therefore, there is a need for a radiation curable adhesive material that, when properly cured, exhibits sufficient adhesion to prevent delamination of the layer during normal use.

WO2002 / 081576

  An object of the present invention is to provide a radiation-cured laminated flexible packaging material that does not leached out residual radiation-curable monomer in its contents and exhibits sufficient adhesion to prevent delamination of the layer during normal use. Is to provide.

  Another object is to form a laminated flexible packaging material whose contents are free of radiation curable monomer leaching and exhibit sufficient adhesion to prevent delamination of the layer during normal use. A radiation-curable adhesive for laminating that can be used as described above is provided.

  The above object and other objects are unexpectedly achieved by using a radiation curable adhesive for bonding which contains a carboxylic acid functional monomer and an organic titanate compound (titanate or titanate). The The present invention provides at least two layers of flexible packaging material bonded together by a radiation-curing laminating adhesive, and provides a novel laminated flexible packaging material suitable for containing pharmaceutical or food grade products. Wherein the radiation curable laminating adhesive is a half-ester formed by reaction of hydroxy (meth) acrylate with an organic anhydride, one or more carboxylic acid functional (meth) acrylates At least 50% monomer and at least one selected from the group consisting of organic titanate, organic zirconate (zirconate or zirconate), organic aluminate (aluminate or aluminate), and organic zinc Contains about 0.1 to about 20%. Organic titanates and organic zirconates are preferred, and organic titanates are most preferred.

  In the present invention, the radiation-curable adhesive for bonding is a half-ester formed by a reaction between a hydroxy (meth) acrylate compound and an organic anhydride. Provided is a novel radiation curable laminating adhesive comprising at least 50% by weight of acrylate and 0.1 to 20% by weight of at least one selected from the group consisting of organic titanate, organic zirconate, organic aluminate, and organic zinc. Is. Organic titanates and organic zirconates are preferred, and organic titanates are most preferred. The present invention also relates to a product packaged with the flexible packaging material.

FIG. 1 shows a cross-sectional view of a radiation-cured laminated flexible packaging material. FIG. 2 shows a cross-sectional view of a radiation-cured laminated flexible packaging material. FIG. 3 shows a cross-sectional view of a radiation-cured laminated flexible packaging material. FIG. 4 shows a side view of the radiation bonding method. FIG. 5 shows a cross-sectional view of the packaged product.

(Radiation curable adhesive for bonding)
The radiation curable laminating adhesive (hereinafter referred to as “radiation curable adhesive composition”) is referred to as one or more carboxylic acid functional radiation curable monomers (hereinafter referred to as “carboxylic acid functional monomers”). .) At least 50% by weight. Preferably, the radiation curable adhesive composition comprises at least 80% by weight of one or more carboxylic acid functional monomers, more preferably at least 90% by weight of one or more carboxylic acid functional monomers. All weight percentages are based on the total weight of the radiation curable composition unless otherwise stated. If desired, the radiation curable composition can include conventional carboxylic acid-free functional monomers, preferably substantially all of the radiation curable monomers of the radiation curable adhesive are: Contains at least one carboxylic acid functional group.

  Preferably, when the radiation curable adhesive is used to form a radiation curable laminate, the carboxylic acid functional monomer is selected such that the laminate exhibits an uncured monomer extraction of less than 50 ppb. To do. As shown in Example 5, one of ordinary skill in the art can readily select a carboxylic acid functional monomer and provide an appropriate extraction value for the desired flexible packaging material.

  Preferably, the carboxylic acid functional monomer has a number average molecular weight of about 100 to about 3,000, more preferably about 150 to about 2,000, and most preferably about 200 to about 1,500. Having a number average molecular weight of The simplest type of carboxylic acid functional monomer is acrylic acid. However, acrylic acid is undesirable because of odor, toxicity, and low molecular weight. Accordingly, preferred radiation curable adhesive compositions are substantially free of acrylic acid.

  One skilled in the art will readily be able to form the desired carboxylic acid functional monomer based on well known reaction mechanisms. For example, using a well-known reaction between a hydroxy functional group and an anhydride, a compound containing both the hydroxy functional group and the desired radiation curable functional group can be reacted with the anhydride to produce the desired carboxyl compound functionality. Monomer can be formed. Without limitation, suitable anhydrides include: phthalic anhydride; maleic anhydride; trimellitic anhydride; tetrahydrophthalic anhydride; hexahydrophthalic anhydride; tetrachlorophthalic anhydride; adipic anhydride Azelaic acid anhydride, sebacic acid anhydride, succinic acid anhydride, glutaric acid anhydride, malonic acid anhydride, pimelic acid anhydride, suberic acid anhydride, 2,2-dimethyl succinic acid anhydride, 3,3- Examples include dimethyl glutaric anhydride; 2,2-dimethyl glutaric anhydride; dodecenyl succinic anhydride; methyl nadic anhydride; octenyl succinic anhydride, and HET anhydride.

  The hydroxy functional group and the compound comprising a radiation curable functional group ("hydroxy functional radiation curable compound") can include any desired radiation curable functional group suitable for the desired application. Preferably, the radiation curable functional group comprises unsaturated ethylene. Examples of suitable unsaturated ethylenes are acrylates, methacrylates, styrenes, vinyl ethers, vinyl esters, N-substituted acrylamides, -vinyl amides, maleates, or fumarates. Preferably, the unsaturated ethylene is provided by an acrylate or methacrylate group. The use of the term “(meth) acrylate” refers to either acrylate, methacrylate, or mixtures thereof.

  Non-limiting examples of suitable hydroxy functional radiation curable compounds containing (meth) acrylate groups include: 2-hydroxyethyl (meth) acrylate; 2-hydroxypropyl (meth) 2-hydroxybutyl (meth) acrylate; 2-hydroxy-3-phenyloxypropyl (meth) acrylate; 1,4-butanediol mono (meth) acrylate; 4-hydroxycyclohexyl (meth) acrylate; Hexanediol mono (meth) acrylate; neopentyl glycol mono (meth) acrylate; trimethylolpropane di (meth) acrylate; trimethylolethane di (meth) acrylate; pentaerythritol tri (meth) acrylate; dipentaerythritol penta (meth) Acrylate; and Is hydroxy-functional (meth) acrylate represented by the following formula:

（式中R１は、水素原子、又はメチル基であり、かつnは1〜5の整数である）。市販されているものの例を挙げると、“Tone”プレポリマー（ドウ ケミカル（Dow Chemical））として売られているヒドロキシ末端（メタ）アクリレートプレポリマーがある。該（メタ）アクリレート化合物は、単一か、又はそれら二つ以上の混合物のどちらでも使用することができる。これらの（メタ）アクリレート化合物のうち、2-ヒドロキシエチル（メタ）アクリレート、及び2-ヒドロキシプロピル（メタ）アクリレートが特に好ましい。ビニルエーテル官能基を有するヒドロキシ官能性放射線硬化性化合物の例を挙げると、例えば、4-ヒドロキシブチルビニルエーテル、及びトリエチレングリコールモノビニルエーテルがある。

(Wherein R1 is a hydrogen atom or a methyl group, and n is an integer of 1 to 5). An example of what is commercially available is the hydroxy-terminated (meth) acrylate prepolymer sold as “Tone” prepolymer (Dow Chemical). The (meth) acrylate compound can be used either alone or as a mixture of two or more thereof. Of these (meth) acrylate compounds, 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate are particularly preferred. Examples of hydroxy-functional radiation curable compounds having vinyl ether functional groups include 4-hydroxybutyl vinyl ether and triethylene glycol monovinyl ether.

Preferably, the radiation curable functional group is an acrylate or methacrylate, with acrylate being most preferred. A particularly preferred carboxylic acid functional monomer is a reaction product of 2-hydroxyethyl acrylate (HEA) represented by the following formula and succinic anhydride.

  Also, if desired, the carboxylic acid functional monomer can be formed by reaction of a suitable dicarboxylic acid functional compound with a hydroxy functional radiation curable compound. However, this method is not preferred because water is generated during the reaction of the hydroxy and carboxylic acid groups, and the water must be removed before using the carboxyl compound monomer of the radiation curable adhesive composition. .

  Also, carboxylic acid functional monomers and oligomers can be formed by various combinations of polyanhydrides and / or polyols. Although not preferred, oligomeric forms of acrylic acid can be used as the carboxylic acid functional monomer, for example, acrylic acid can be dimerized or trimerized by well-known self-addition reactions. The oligomer can be formed. A stable dimeric compound is beta carboxyethyl acrylate (“BCEA”). However, BCEA is usually not preferred because it contains residual amounts of acrylic acid.

  One skilled in the art could readily formulate the radiation curable adhesive composition to provide the proper viscosity for the desired application. Generally, the viscosity of the radiation curable adhesive composition should be low (eg, about 3,000 centipoise or less) at the application temperature to facilitate application to the web. Usually, the application temperature is room temperature (25 ° C.). However, higher application temperatures can be utilized as desired. Preferably, the carboxylic acid functional monomer has a low viscosity to avoid the use of dilution monomers and provides a suitable viscosity for applying the radiation curable adhesive to a layer of flexible packaging material. A suitable viscosity for the carboxyl compound functional monomer is from about 50 to about 10,000 centipoise at the application temperature, and more preferably from about 100 to about 5,000 centipoise at the application temperature.

  Also, certain combinations of carboxylic acid functional monomers have been found useful because they improve their adhesion and reduce migration. In particular, monomers formed from the reaction of hydroxy acrylates with substituted alkene succinic anhydrides or phthalic anhydrides are useful in formulations that improve the water resistance of the finished laminate. The monomer can be used in various proportions. The preferred ratio will depend on the particular material to be bonded, as shown in Example 5. One of ordinary skill in the art can readily select an appropriate combination of carboxylic acid functional monomers based on the description herein without undue experimentation, and the desired layers of flexible packaging material can be selected as desired. Migration and adhesion could be provided.

  When the radiation curable adhesive is blended so as to be cured by exposure to visible light, ultraviolet light, or the like, as a polymerization initiator for increasing the curing rate, one or more photoinitiators and / or photosensitizers Can be used. Without limitation, examples of suitable photoinitiators and photosensitizers include: 2,2 '-(2,5-thiophendiyl) bis (5-tertiary-butybenzoxazole); 2,2-dimethoxy-2-phenylacetophenone; xanthone; fluorenone; anthraquinone; 3-methylacetophenone; 4-chlorobenzophenone; 4,4'-dimethoxybenzophenone; 4,4'-diaminobenzophenone; Michler's ketone; Benzophenone; benzoin propyl ether; benzoin ethyl ether; benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one; 2-hydroxy-2-methyl-1-phenylpropane-1 -On; methylbenzoylformate thioxanthone; diethyl thioxanthone; 2-isopropylthio Sandton; there is and 2,4,6-trimethylbenzoyl diphenylphosphine oxide; 2-chlorothioxanthone; 2-methyl-1- (4- (methylthio) phenyl) -2-morpholino-1-one. Examples of those that are commercially available include IRGACURE 184, 369, 500, 651, 819, 907, and 2959, and Darocur 1173 (Ciba Geigy); Lucirin TPO (BASF); and Ebecryl P36 , And P37 (UCB co.).

  Preferably, a photopolymerization initiator is utilized in the radiation curable adhesive composition. Furthermore, the use of the photoinitiator reduces the possibility of migration of the photoinitiator or the photoinitiator residue. Without limitation, examples of suitable photoinitiators include the commercially available KIP100, KIP150, and EsacureKK (Lamberti).

  If desired, one or more photoinitiators and / or photosensitizers can be mixed into the radiation curable adhesive paint in an amount of about 0.1 to about 10% by weight of the total composition. . Photoinitiators are generally not beneficial if the radiation curable adhesive composition is formulated to be exposed to an electron beam and utilize a radical curing system. However, in cationic curing systems, photoinitiators are beneficial even when curing with an electron beam. Based on the description herein, those skilled in the art of formulating radiation curable adhesive compositions can readily formulate according to a suitable curing system for the desired application without undue experimentation. .

  The radiation curable adhesive may contain a radiation curable oligomer. Normally, with respect to the molecular weight of the monomer, oligomers are not related to migration because of these higher molecular weights. (Meth) acrylate functional oligomers are preferred. Without limitation, these are sold under the name Epoxy (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate oligomer, acrylic derivative oligomer with (meth) acrylate, and the trade name Sarbox (Sartomer) And oligomers having (meth) acrylates based on maleic anhydride copolymers.

  By mixing one or more titanate compounds, the adhesive composition can be formulated to give improved adhesion strength and improved water resistance when properly cured in a laminated structure. Although a wide variety of titanate compounds can be used, certain titanates are preferred due to their stability in the presence of carboxylic acid functional monomers. Certain titanates also provide excellent adhesion. Useful levels of titanate compounds are about 0.1 to about 20% by weight, preferably about 1 to about 15% by weight, based on the total weight of the composition.

  Organic titanates are a well-known compound species. The two main species of organic titanates are tretra alkyl titanates and titanate chelates. Terraalkyl titanates have the general structure Ti (OR) 4, where R is the residue of an organic alcohol such as isopropyl alcohol, n-butanol, 2-ethylhexyl alcohol, and the like. The organic portion of the titanate chelate has one or more active sites that can coordinate to titanium. Examples of the organic portion of the titanate chelate include triethanolamine, acetoacetonate, and ethyl acetoacetate. For discussion of organic titanates, use the General Brochre for Tyzor, a trade name Tyzor product available from DuPont.

  Several commercial uses of organic titanates are known. These include catalysts for esterification reactions, surface modification of organic and inorganic materials, gel-sol forming reagents, and polymeric crosslinkers. In the radiation-curable adhesive composition for laminating of the present invention, the use of the organic titanate has not been known so far.

  The present invention relates to mixing organic titanate compounds in a radiation curable adhesive for bonding applied to a packaging material. In particular, we have found the advantage of mixing organic titanate compounds based on carboxylic acid functional monomers. The main advantage of the organic titanate compound is that it provides strong adhesion in the laminated packaging material together with moisture resistance and chemical resistance.

  A commercial example of an organic titanate mixed with a carboxylic acid functional monomer is KR 39DS (Kenrich Petrochemicals). This organic titanate has three acrylic acid groups and one diethylene glycol monomethyl ether group. However, when this titanate is mixed into an adhesive formulation containing added carboxylic acid functional monomers, the acidic groups will release free acrylic acid and reach equilibrium. Acrylic acid is undesirable and rather should be avoided due to odor, toxicity, and low molecular weight issues.

  We have found it advantageous to use organic titanate compounds based on carboxylic acid functional monomers that are substantially free of acrylic acid. These include carboxylic acid functional monomers that are the reaction product of the hydroxy (meth) acrylate compound described above and an organic anhydride.

  The desired organic titanate compound can be formed by reaction of the carboxyl compound functional monomer with an alkyl titanate. This includes substitution of the corresponding alkyl alcohol and evaporation. For example, a half-ester of 2-hydroxyethyl acrylate and succinic anhydride may be reacted with tetraisopropyl titanate. This reaction is driven by evaporation of isopropyl alcohol. In some instances, it is desirable to use an organic titanate that has both a chelating group and an alkyl group. An example is bis-triethanolamine diisopropyl titanate. In this case, one would expect that only the isopropyl alcohol group would be replaced by the carboxylic acid monomer.

  These compounds formed by the reaction of hydroxy (meth) acrylate-anhydride half-esters with alkyl titanates are novel materials. The new carboxylic monomer titanate compound may be prepared and isolated as shown in Example 1. Alternatively, these compounds may be formed in situ by mixing the desired organic titanate into the adhesive formulation containing a carboxylic acid functional monomer as shown in Examples 3-7. Usually, for food applications, it is undesirable for free alkyl alcohol to be present in the adhesive. In such a case, the alcohol can be dissipated from the mixture by heating, mixing, spraying, or processing the mixture under reduced pressure.

  Also, instead of the organic titanate, organic zirconate, organic aluminate, and / or organic zinc will provide improved adhesion in the presence of the adhesive composition. However, organic titanates and organic zirconates are preferred, and organic titanates are most preferred. Radiation curable adhesives also contain additives, such as fillers, flow agents, antifoam agents, pigments, dyes, or dispersed or solubilized resinous materials in the composition. You may go out. The selection and use of such additives is within the skill in the art.

When properly cured, the carboxylic acid functional monomer used in the present invention is an unexpected combination with sufficient adhesion to a low surface energy layer, such as a polyolefin protective film, to prevent delamination. And has been found to substantially prevent migration through the layer in an uncured free-monomer form.
The radiation curable adhesive composition can also be used to form an improved laminated flexible packaging material as described below.

(Laminated flexible packaging material)
The formation of the laminated flexible packaging is well known and therefore will not be discussed in detail herein. Using conventional techniques and replacing the conventional laminating adhesive with the radiation curable laminating adhesive described herein, the new laminated flexible packaging material described herein is Can be manufactured easily. Preferred methods of applying the radiation curable adhesive include the use of well known web coating methods such as roll coating, gravure, offset gravure and the like. As desired, the adhesive may be applied and cured off-line with the print, either in-line or in individual laminates.

  When using a low surface energy layer, such as a polyolefin, the surface of the adhered layer is preferably surface treated to increase adhesion. Surface treatments are well known and any conventional surface treatment method can be used as desired in a particular application. Examples of suitable surface treatment methods include corona treatment, chemical treatment, plasma, and flame treatment. Preferably, if a polyolefin-based layer is utilized, a corona treatment or flame treatment is first applied to the surface prior to bonding with the radiation curable adhesive.

  The laminated flexible packaging material will be described with reference to FIGS. 1-3, the laminated flexible packaging material 20 includes at least one flexible packaging material second layer 22 laminated to the flexible packaging material first layer 26 by the novel radiation curable adhesive 24, Here, the layer 26 is a layer that becomes the inner side of the finished packaging material. The laminated flexible packaging material 20 can also include other layers as desired. Examples of suitable materials for the at least one second layer 22 and the first layer 26 include, but are not limited to, paper, aluminum foil, vapor-deposited film, coating film, printed film, coextruded film, polyester film , Polyolefin base films, white polyolefin base films, polyamide base films, copolymer films, and films containing various polymer blends. Preferably, the first layer 26 is polyolefin based.

  The radiation curable laminating adhesive described herein can be used to provide improved laminated flexible packaging, substantially reducing the problem of contamination due to monomer migration. The carboxylic acid monomer of the radiation curable adhesive composition is found to have a sufficiently low migration through the layer of flexible packaging material (especially polyolefin) than the monomer used in conventional radiation curable adhesives. Has been issued. Also, when properly cured to prevent delamination of the laminated flexible packaging material during use, the carboxylic acid monomer used in the present invention provides sufficient adhesion to various packaging materials. Has been found.

  The radiation curable adhesive composition described herein can be applied and cured using conventional techniques (eg, UV light of a medium pressure mercury lamp that passes directly through the layer). . When ultraviolet (UV) light is used for curing the radiation curable adhesive composition, the UV curable adhesive is not substantially prevented from being absorbed or blocked by preventing the radiation curable adhesive from being cured. Or a polymeric material that does not inhibit should be selected. Thus, when UV curing is desired, preferably at least one of the second layer 22 or the first layer 26 is substantially transparent. The substantially transparent layer 22 can be formed from any suitable material. Examples of suitable polymeric materials that are substantially transparent include polyolefins, polyesters, and polystyrenes. Preferably, the layer 22 is formed from a polyolefin.

  Alternatively, electron beam irradiation (EB) may be used to cure the radiation curable adhesive composition. When utilizing curing with EB, the layer 22 and the layer 26 need not be substantially transparent. Without limitation, if a polyolefin is used for the layer 22 and / or examples of suitable polyolefins for use in the preferred layer 26, homopolymers or copolymers such as ethylene, butylene, propylene, hexene, octene, etc. There is. Preferred polyolefin base films include polypropylene and polyethylene such as high density polyethylene (HDPE) or linear low density polyethylene (LLDPE), polyisobutylene (PIB). Polypropylene stretch forms, such as biaxial stretch (BOPP) or stretched polypropylene (OPP), can be used as desired.

  If desired, the polyolefin used in layer 22 or layer 26 can be coated, blended, copolymerized, or coextruded with other materials to enhance barrier, handling, appearance, or sealability. Can be molded. These modifications are included in the definition of “polyolefin-based” and “polyolefin-containing” for the layer 22 or 26. Common coatings include polyvinylidene chloride (PVdC), acrylic derivative based coatings, and various other barrier and heat seal coatings. The polyolefin can also receive a thin layer of metal using vacuum deposition. Common polyolefin copolymers used to make flexible packaging films include ethylene and vinyl acetate (EVA), and copolymers of ethylene and vinyl alcohol (EVOH), ethylene and acrylic acid, ethylene and ethyl acrylate. Despite the fact that many of these modifications are known and improve the barrier properties of polyolefins, there are still migration-resistant laminating adhesives that prevent unpleasant odors and odors in packaged products. It is desired.

  In addition, examples of suitable layers in the use of laminated flexible packaging materials are identified in US Pat. No. 5,399,396, which is incorporated herein by reference. Other suitable layers are described in Diane Twede and Ron Goddard "Packaging Materials" 2nd edition, Pira International, Surry, UK 1998.

  Another example of the laminated flexible packaging material is shown in FIG. The laminated flexible wrapping includes a transparent layer 26 comprising a polyolefin that is a back print 28 on its inner surface, and then the layer 22 is adhered using the radiation curable adhesive composition 24. In this type of packaging material, the printing material is made readable on the inner surface of the packaging material.

  As shown in FIG. 3, another example of a laminated flexible packaging material includes a transparent layer 22 that is a back print 28 on its inner surface, and then using a radiation curable adhesive composition 24, Glue layer 26. In this type of packaging material, the printing material is made readable on the outer surface of the packaging material.

  Although not shown in the figure, further, an example of a laminated flexible packaging material was bonded together with the radiation curable adhesive composition to a white polyolefin layer having a printing material on its outer surface. There is a transparent layer. The printing can be done using any conventional method, such as the well-known ink and / or electrophotographic techniques. Preferred methods include using flexographic or gravure printing machines that apply prints in continuous lines.

  The layer 22, layer 26, and adhesive layer 24 can be made to any thickness as desired in a particular application. For example, typically, the layer 22 is about 0.1-5 mils thick, preferably about 0.3-3 mils thick. Typically, the adhesive layer 24 is about 0.03 to about 1 mil thick, preferably about 0.05 to about 0.2 mil thick. Typically, the layer 26 is about 0.1 to about 5 mils thick.

  The laminated flexible packaging material can be formed using any conventional method. FIG. 4 shows an example of a radiation laminating method for forming a 2-layer flexible laminated packaging material and an arbitrary 3-layer flexible laminated packaging material. Many layers can be bonded together using the radiation curable adhesive of the present invention.

  Unwind the first layer 101 of flexible packaging material. The first layer 101 can be fed directly from a roll or a printing press used to apply the drawings to the packaging material. The adhesive paint 103 is applied to the layer 101 using the application roller 102 to form an adhesive paint layer 104. This is a simplified diagram. Various types of roll coating methods can be used, including methods using up to about 6 rollers. The adhesive reservoir containing the adhesive paint 103 can be opened and closed. Also, wet adhesive can be pumped from the supply system. The adhesive application system, including the adhesive 103 and the roller 102, may be heated to ambient temperature or to a desired application weight and flowability to facilitate.

  The second layer 105 of the flexible packaging material is unwound and attached to the adhesive paint layer 104 using a nip roller 106 to form a two-layer laminate 107. The nip roller 106 can be made of a variety of different materials including, for example, rubber, steel, and ceramic. The roll pressure can be set for best performance and appearance. The roller 106 may be at ambient temperature or heated.

  An optional second laminating adhesive application roller 108 can be used to apply the second adhesive paint 109 to form the adhesive paint 110 on the laminate 107. The third layer 111 of any flexible packaging material is unwound and applied to the adhesive paint 110 using an optional second set of lamination nip rollers 112 to form a 3-layer laminate 113.

  Next, an electron beam generator or a UV lamp device 114 applies accelerated electrons to the laminate 113 or irradiates UV to cure at least one of the adhesive paints 104 and / or 110. . If UV is used, the flexible wrapping layer must be at least partially transparent to UV to cure the adhesive. Since accelerated electrons can pass through the opaque layer of packaging material, EB can be used for opaque or printed material. In order to cure the adhesive, the EB acceleration potential should be high enough to penetrate at least the layers of the packaging material. The device should be shielded so that workers are not exposed to the UV light or secondary X-rays associated with EB generation. Any spare roller, or beam dump 116, can be cooled to suppress excessive heat in the curing process.

  Electron beam generators commercially available from a number of vendors including Energy Science Inc. (ESI) and Advanced Electron Beams (AEB) can be used. The transmission of electrons into the packaging material is determined by the acceleration potential of the beam. In general, a potential range of about 60-250 KV is appropriate for the bonding of most flexible packaging materials. Preferably, it is in the range of about 70-170 KV. The total electron beam energy (dose) applied to the material is measured in units of Mrad. A dose range of about 0.5 to 6.0 Mrad is suitable for curing the adhesive of the present invention. Preferably, the dose ranges from about 1.0 to 4.0 Mrad.

  The cured laminate 117 can be advanced to any post-cured web processing, which typically includes trimming, slitching, and / or sheeting. The cured laminate 117 can be rewound to form a roll 119 with respect to the laminated web of packaging material. Preferably, both adhesives 104 and 110 are radiation curable adhesives of the present invention. However, if desired, one of the adhesives may be non-radiation curable. In a multilayer laminate, at least one of the adhesive layers must contain the radiation curable adhesive of the present invention. A radiation curable adhesive must be applied before the curing device 114. The non-radiation curable adhesive can be applied before or after the curing device 114. This is a simplified diagram for illustrative purposes. Typically, other web processing, cleaning, handling, and paint appendages are parts or methods.

  Rapid EB or UV curing allows for quick in-line processing. However, in-line processing using another type of bonding adhesive is difficult because the adhesive does not cure sufficiently in a short time. The improved laminated flexible packaging can be used to wrap beverages, drugs, medical and dental devices, and food. Preferred examples include snack food packaging, mixed instant dried food, meat packaging, cheese packaging, and flavored beverage containers. It would also be desirable to use the improved laminated flexible packaging for non-food industry or consumer packaging. Although the flavor or migration may not be relevant for non-food use, the rapid adhesion and delamination resistance achieved with these new radiation curable laminating adhesives Would be desirable. Examples of industrial and non-consumer food applications include wet and dry wipe product packaging.

  The package can be formed using any conventional method. A cross-sectional view of the packaged material 120 within the flexible packaging material 122 is illustrated in FIG. The edge 124 of the flexible wrap 122 can be sealed using any conventional sealing method, such as a heat sealing method using an adhesive or a cold sealing method, as desired.

  The invention will now be described with reference to the following non-limiting examples and comparative examples. The migration of carboxylic acid functional monomers of the radiation curable adhesive composition is tested using food industry standards. The test results clearly show that the migration of the carboxylic acid functional monomer through the layered flexible wrapping layer is sufficiently lower than the monomers utilized in conventional radiation curable adhesives. It was. Accordingly, the improved radiation curable adhesive composition provides an adhesive layer that sufficiently reduces the risk of migration of uncured monomer through the flexible packaging layer and contamination of the uncured monomer to the packaged product contents. Can be provided.

  Test results also revealed that the radiation curable adhesives of the present invention exhibit improved adhesion and delamination resistance (especially when flowable) when properly cured. The following examples illustrate the new and improved adhesive compositions of the present invention.

Example 1
By reaction of 4.4 molar equivalents of carboxylic acid functional monomer (HEA-succinate monomer), which is a half-ester with 2-hydroxyethyl acrylate (HEA) and succinic anhydride, and 1.0 molar equivalent of titanium tetraisoproxide A UV / EB curable titanate compound was prepared. The mixture was heated under reduced pressure to remove isopropyl alcohol. The resulting product was a viscous, reddish clear liquid. The dry ash was heated and weighed as TiO2, and the determined titanium content was 4.8%. This is in good agreement with the theoretical value of 4.8% of the predicted titanium content, indicating that the product is a new titanate compound with 4 moles of HEA-succinate bound per mole of titanate. Show.

(Example 2)
The organic titanate compound of Example 1 was used in the adhesive formulation shown in Table 1. For comparison, the "A" formulation did not contain titanate. Approximately 0.1 mil of thin film of each adhesive was applied to various flexible packaging layers. The wet adhesive was applied to the second layer of the flexible packaging material, and the resulting laminate was cured by EB irradiation (165 kV, dose 3.0 Mrad). The adhesion strength of the resulting laminate was measured using a tensile tester at a speed of 30.48 cm (12 inches) / min in a T-type peel configuration. The results are shown in the table below. The results show that the adhesion strength of the oPP / deposited oPP laminate is enhanced in the presence of the titanate compound. The results also show that the titanate improves the water resistance of the two polyester (PET) film layers.

(Example 3)
A series of titanate compounds were mixed into a UV curable adhesive for bonding as shown in Table 2. The adhesive was applied to a polypropylene film at a thickness of about 0.2 mil. A second layer of polypropylene film was placed over the wet adhesive. The UV was then exposed from the film tip using a 300 w / 0.025 m (1 inch) medium pressure mercury arc lamp at a conveyor speed of 30.48 m (100 ft) / min to form a laminate. The adhesive was cured. The adhesive strength of the laminate was measured by a T-type peel test. The results show a significant increase in bond strength in all cases where the titanate is present. About stability, it confirmed that it could be stored for one month at room temperature. The mixture containing triethanolamine titanate remained liquid, did not precipitate (ppt), and there was no significant change in viscosity.

Example 4
The reaction product of triethanolamine titanate up to 4.0 percent, 1 equivalent of benzophenone dianhydride and 2 equivalents of caprolactone-based hydroxyacrylate (Tone M-100), up to 10 percent of difunctional monomer, and bifunctional An experimental design was conducted to evaluate the adhesive composition containing up to 15 percent aromatic urethane acrylate oligomer (Sartomer CN 973). The balance of the formulation was composed of HEA-succinate monomer. The test formulation was applied onto the inner packaging layer web using an offset gravure coater. The weight of the adhesive was adjusted to 0.54 + 0.09 kg (1.2 + 0.2 lb) /278.7 m 2 (3,000 ft 2). The outer packaging web was sandwiched between the wet adhesives. The moving web was then exposed to an electron beam (165 kV, dose 3.0 Mrad) to cure the laminate. The adhesive strength of the laminate was measured by a T-type peel test. Table 3 shows the optimum adhesive formulation obtained from the T-peel data analysis. The results show the advantages of the titanate compound in the adhesive formulation.

(Example 5)
An experimental design was conducted to evaluate an adhesive composition containing three different types of monomers that are half-esters of 2-hydroxyacrylate (HEA) and acid anhydride. The three types of anhydrides were succinic anhydride, phthalic anhydride, and 2-dodecenyl succinic anhydride (DSA). The composition contained at least 20% HEA-succinate, up to 80% HEA-phthalate, up to 80% HEA-DSA, and up to 8% triethanolamine titanate. All compositions contained 0.2% of a fluorosurfactant. The adhesive was applied and cured in the manner described in Example 4. After immersing a long piece of 0.025 m (1 inch) wide in water for 1 hour, a T-type peel test was immediately performed to measure the water resistance of the laminate. Table 4 shows the optimum adhesive formulation obtained from the T-peel data analysis. For comparison, the results of T-peeling of 96% HEA-succinate and 4% triethanolamine titanate blend are shown. The results show that it is significant to have HEA-succinate and HEA-dodecenyl succinate monomers in the formulation to achieve improved water resistance.

(Example 6)
An adhesive formulation was prepared containing 94.9% by weight HEA-succinate, 4% triethanolamine titanate, and 0.1% fluorosurfactant. The adhesive was applied onto a web of coextruded packaging film based on ethylene vinyl alcohol copolymer (EVOH) and linear low density polyethylene (LLDPE). The web of polyester (PET) packaging film was sandwiched between the wet adhesive and the adhesive was exposed by exposing the moving web through the PET side using an electron beam (110 kV, dose 3.0 Mrad). Cured to form a laminate. The laminate was extracted from the LLDPE side using Miglyol 812 for 2 hours at 66 ° C., followed by 238 hours at 40 ° C. This protocol is approved by the FDA as a method of testing the suitability of packaging materials applied to food. The test was performed in triplicate in an independent laboratory and confirmed with appropriate controls. With a detection limit of 50 PPB, no adhesive component was detected in the extract.

(Example 7)
Five adhesive formulations were prepared as shown in Table 5. The adhesive was used to bond two layers of 0.7 mil oriented polypropylene (oPP) film. The adhesive was applied and cured with EB using the procedure described in Example 4. All attempts to separate the oPP film resulted in the oPP film tearing quickly. This demonstrates the excellent adhesion of the adhesive. The laminated film was stacked in a single-sided test cell containing 10 milliliters of 95% ethanol for each 6.5 cm 2 (1.0 square inch each) of the lamination area. The laminate was extracted at 40 ° C. for 10 days. This is a test protocol approved by the FDA as a method of determining the suitability of packaging materials used in food applications. Table 5 shows the results of extraction of the three types of adhesive components. The important points revealed from this example are: 1) The importance of high levels of carboxylic acid monomers to achieve low extractivity (A, B, C all carboxylic acid functional monomers are D ( 59.8%), 91.8% compared to E (39.8%).); 2) Advantage of using multiple carboxylic acid functional monomers in the formulation (A vs. B and C extractables) Compare results); and 3) The high level of extracted trimethylolpropane triacrylate (TMPTA) monomer is related to the very low extractables of the carboxylic acid functional acrylate monomers (HEA-succinate and HEA-phthalate) . In this example, the carboxylic acid functional monomer is monofunctional while TMPTA is a trifunctional monomer. One skilled in the art would expect lower extraction amounts with multifunctional materials. Thus, the low extractable amount of carboxylic acid functional monomer is unexpected and unexpected.

(Example 8)
An organic zirconate compound based on HEA-succinate monomer was prepared by DuPont under the experimental name TLF-9566. This organic zirconate was used in the adhesive formulation shown in Table 6. As a comparison, the zirconate was not included in the “A” formulation. A thin film (about 0.1 mil) of each adhesive was applied to various layers of flexible packaging. The wet adhesive was applied to the second layer of the flexible packaging material, and the resulting laminate was cured by EB irradiation (165 kV, dose 3.0 Mrad). The adhesive strength of the obtained laminate was determined by a T-type peel test. The results are shown below Table 6. The results show that the adhesion strength of the oPP / deposited oPP laminate is enhanced in the presence of the zirconate compound. The results also show that the zirconate improves the water resistance of the two polyester (PET) film layers.

  The test results allow the improved radiation curable adhesive composition to provide an adhesive layer having improved adhesion and substantially transfer through the packaging of uncured monomer and packaging To reduce the risk of contamination of uncured monomers in the finished product content.

  Although the claims of the present invention have been described in detail and with reference to specific embodiments thereof, various changes and modifications may be made to the claims of the invention without departing from the spirit and scope thereof. It will be understood in the art that this can be done.

Claims (4)

Radiation curable adhesive for laminating:
a) at least 80% by weight of one or more carboxylic acid functional (meth) acrylate monomers that are half-esters formed by reaction of a hydroxy (meth) acrylate compound with an organic anhydride, and b) 0.1% of an organic zirconate. The radiation curable laminating adhesive comprising ~ 20% by weight. Radiation curable adhesive for laminating:
a) at least 80% by weight of one or more carboxylic acid functional (meth) acrylate monomers that are half-esters formed by reaction of a hydroxy (meth) acrylate compound with an organic anhydride, and b) an organic zirconate, organic The radiation-curable adhesive for bonding, comprising 0.1 to 20% by weight of at least one selected from the group consisting of aluminate and / or organic zinc. A laminated flexible packaging material comprising at least two layers of a flexible packaging material bonded together by a radiation-curing laminating adhesive, the radiation-curing laminating adhesive comprising:
a) at least 80% of one or more carboxylic acid functional (meth) acrylate monomers that are half-esters formed by reaction of a hydroxy (meth) acrylate compound with an organic anhydride, and b) about an organic zirconate compound. The radiation curable laminating adhesive comprising 0.1 to about 20%. A laminated flexible packaging material comprising at least two layers of a flexible packaging material bonded together by a radiation-curing laminating adhesive, the radiation-curing laminating adhesive comprising:
a) at least 80% of one or more carboxylic acid functional (meth) acrylate monomers, which are half-esters formed by reaction of hydroxy (meth) acrylate compounds with organic anhydrides, and b) organic zirconates, organic aluminum The radiation curable laminating adhesive comprising about 0.1 to about 20% of at least one selected from the group consisting of nate and organozinc.

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