Patent Application
20230167340
The present invention relates to a solvent-based laminating adhesive composition; and to a process of preparing such laminating adhesive composition.
Laminating adhesives are used to bond different substrates together. A common usage of such bonded substrates is in flexible food packaging applications. The laminating adhesive is typically applied to the surfaces of two polymeric substrate layers to form a bonding layer in between the two substrate layers. The adhesive forms a bonding layer inbetween the substrate layers to provide a strong bond between the two substrate layers. The adhesive-bonded substrates structure helps keep the packaging structure intact; and the food inside the packaging structure safe and secure. A growing demand in the flexible food packaging industry is for a laminating adhesive with good gas barrier properties such as to reduce oxygen permeability through the layered structure of the flexible food packaging. Laminating adhesives that are used to produce a layered food package structure exhibiting a reduced oxygen permeability could potentially simplify packaging structures, reduce cost-in-use, and make the food package recyclable. It is therefore desirous to provide a laminating adhesive with enhanced oxygen barrier performance such as an adhesive demonstrating a low oxygen permeability compared to standard adhesive. In particular, it is desirous to provide a laminating adhesive based on crystalline polycarbonate compounds such that the adhesive has a gas barrier effect/property.
An objective of the present invention is to provide a laminating adhesive useful for flexible packaging applications, wherein the laminating adhesive has an enhanced oxygen barrier performance compared to standard adhesives; and a process for producing such laminating adhesive.
In one embodiment, the present invention is directed to a two-component, solvent-based polyurethane laminating adhesive composition, wherein the adhesive composition is based on a crystalline polycarbonate and wherein the adhesive composition is useful for producing a multi-layer laminate structure. The adhesive composition includes, for example: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive component comprising a reaction product of: (bi) at least one crystalline polycarbonate diol compound, (bii) at least one flow modifier agent, such as an acrylic polymer compound, and (biii) optional additives, if desired; and (c) at least one solvent.
In another embodiment, the present invention is directed to a process for preparing the above adhesive composition.
In still another embodiment, the present invention is directed to a multi-layer laminate product including: (A) at least a first layer; (B) at least a second layer; and (C) at least one layer of the above adhesive composition disposed inbetween the first layer and the second layer; and wherein the adhesive composition is cured to bond the first layer to the second layer.
In yet another embodiment, the present invention is directed to a process for producing the above multi-layer laminate product.
In even still another embodiment, the present invention is directed to a packing product produced using the above multi-layer laminate product.
As used throughout this specification, the abbreviations given below have the following meanings, unless the context clearly indicates otherwise: “<” means “less than”; “>” means “greater than”; “≤” means “less than or equal to”; ≥” means “greater than or equal to”; “@” means “at”; μm=micron(s), g=gram(s); mg=milligram(s); L=liter(s); g/cc=gram(s) per cubic centimeter; mL=milliliter(s); g/mL=gram(s) per milliliter; g/mol=gram(s) per mole; g/m2=gram(s) per square meter; ppm=parts per million; ppmw=parts per million by weight; rpm=revolutions per minute; m=meter(s); mm=millimeter(s); cm=centimeter(s); cm/min=centimeter(s) per minute; min=minute(s); s=second(s); hr=hour(s); ° C.=degree(s) Celsius; N=Newtons; mmHg=millimeters of mercury; psig=pounds per square inch; ccO2/m2/day=cubic centimeters of oxygen per [square meter-day]; N/15 mm=Newton(s) per 15 millimeters; kPa=kilopascal(s); %=percent, vol %=volume percent; and wt %=weight percent.
Unless stated otherwise, all percentages, parts, ratios, and like amounts, are defined by weight. For example, all percentages stated herein are weight percentages (wt %), unless otherwise indicated.
Temperatures are in degrees Celsius (° C.); and “ambient temperature” and/or “room temperature” means a temperature between 20° C. and 25° C., unless specified otherwise.
The present invention is directed to a novel two-component, solvent-based polyurethane adhesive composition, wherein the adhesive composition is based on a crystalline polycarbonate and wherein the adhesive composition is useful for producing an adhesive laminate structure. The adhesive composition includes, for example: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive component comprising a reaction product of: (bi) at least one crystalline polycarbonate diol compound; (bii) at least one acrylic polymer compound; and (biii) at least one solvent.
In general, to prepare the two-part laminating adhesive composition includes providing a first part comprising the isocyanate component, component (a); providing a second part comprising the isocyanate-reactive component, component (b), such as for example a polyol component; and then combining or mixing together component (a) and component (b) to form the two-part adhesive system or composition.
The isocyanate component, component (a), of the present invention can include one or more isocyanate compounds. For example, the isocyanate compound can include aliphatic-based isocyanates, aromatic-based isocyanates, and mixtures thereof. An aliphatic-based polyisocyanate is an isocyanate that contains no aromatic rings. Examples of suitable aliphatic isocyanates useful in the present invention include, but are not limited to, hexamethylene diisocyanate (HDI); diisocyanatodicyclohexylmethane (H12MDI); xylylene diisocyanate (XDI); 1,4- or 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI); tetramethylxylylene diisocyanate; dimers, trimers, derivatives and mixtures of two or more thereof.
The aromatic-based isocyanate useful in the present invention can include, for example, one or more polyisocyanate compounds including, but are not limited to 1,3- and 1,4-phenylene diisocyanate; 1,5-naphthylene diisocyanate; 2,6-toluene diisocyanate (2,6-TDI); 2,4-toluene diisocyanate (2,4-TDI); 2,4′-diphenylmethane diisocyanate (2,4′-MDI); 4,4′-diphenylmethane diisocyanate (4,4′-MDI); polymeric isocyanates; and mixtures of two or more thereof.
In one preferred embodiment, the isocyanate component useful in the present invention can be XDI based polyisocyanate; HDI-based polyisocyanate; MDI based polyisocyanate; TDI-based polyisocyanate, and mixtures thereof.
Exemplary of some commercial isocyanate components useful in the present invention can include TAKENATE® D-110N and TAKENATE® D-120N (both available from Mitsui Chemical); DESMODUR® N 3300, DESMODUR® Quix 175, and DESMODUR® E 2200/76 (all available from The Covestro Company; and ISONATE™ 125 M, ADCOTE™ L76-204, COREACTANT CT, and CATALYST F (all available from The Dow Chemical Company); and mixtures thereof.
The isocyanate has an average functionality of greater than 2 isocyanate groups/molecules. In one embodiment, for instance, the isocyanate may have an average functionality of from 2.1 to 4.0.
A compound having isocyanate groups, such as the isocyanate component (a) of the present invention, can also be characterized by a weight percentage of isocyanate groups (NCO) based on a total weight of the compound. The weight percentage of isocyanate groups is termed “% NCO” and is measured in accordance with ASTM D2572-97. In one embodiment, the NCO content of component (a) is 7% or more; and 10% or more in another embodiment. In still another embodiment, the NCO content of component (a) is 30% or less; and 25% or less in yet another embodiment.
The amount of the isocyanate component used in the present invention process is, for example, from 2 wt % to 40 wt % in one embodiment, from 3 wt % to 30 wt % in another embodiment and from 4 wt % to 20 wt % in still another embodiment.
The isocyanate-reactive component, component (b) (or the B-side component) of the present invention, includes an isocyanate-reactive composition which is a reaction product of: (bi) a predetermined amount of at least one crystalline polycarbonate diol compound; and (bii) a predetermined amount of at least one acrylic polymer compound; and (biii) a predetermined amount of at least one solvent. The blend or mixture of the above three components (bi)-(biii) forms the isocyanate-reactive component (b) that is mixed with the isocyanate component (a). The polyurethane adhesive composition based on a crystalline polycarbonate for producing an adhesive laminate structure is formed by mixing component (a) with component (b).
Component (a) can be mixed with component (b) at a weight ratio of from 4:100 to 30:100 in one embodiment; from 5:100 to 25:100 in another embodiment; and from 6:100 to 20:100 in still another embodiment.
A crystalline polycarbonate diol is a compound that has the structure of carbonate unit and hydroxyl terminated groups, and is solid over the temperature range that includes the range of 10° C. to 40° C. Examples of suitable crystalline polycarbonate diol useful in the present invention include, but are not limited to, poly(hexanediol-carbonate), poly(butanediol-carbonate), and mixtures of two or more thereof.
In one preferred embodiment, the crystalline polycarbonate diol has a melting temperature of 35° C. to 60° C. and molecular weight of 500 g/mol to 3,500 g/mol.
Exemplary of some of the commercial crystalline polycarbonate diol compounds useful in the present invention can include, for example, ETERNACOLL®UH-100, ETERNACOLL®UH-200 and ETERNACOLL® UH-300 available from UBE Industries, Inc.
The amount of the crystalline polycarbonate diol compound used to make isocyanate-reactive co-reactant, component (b), of the present invention process is, for example, from 10 wt % to 50 wt % in one embodiment, from 15 wt % to 45 wt % in another embodiment and from 20 wt % to 40 wt % in still another embodiment.
The at least one acrylic polymer compound, component (ii), useful in the present invention is a flow modifier or a flow control agent which are typically used in powder coatings to control cratering and reduce orange-peel characteristics. Flow modifiers help control interfacial tension and surface tension of the adhesives.
The flow modifier useful in the present invention can include one or more common flow modifiers, for example, low glass transition temperature acrylics such as polylauryl acrylate, polybutyl acrylate, poly(2-ethylhexyl) acrylate, poly(ethylacrylate-2-ethylhexylacrylate), polylauryl methacrylate, acrylic copolymer made of two or more monomers, including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene, vinyl acetate, butadiene and the like; and mixtures thereof. Other useful flow modifiers can include silicon-containing polymers and fluorinated polymers, such as the esters of polyethylene glycol or polypropylene glycol, and fluorinated fatty acids.
The amount of the acrylic polymer compound used to make isocyanate-reactive co-reactant, component (b), of the present invention process is, for example, from 0.05 wt % to 4 wt % in one embodiment, from 0.1 wt % to 3 wt % in another embodiment and from 0.2 wt % to 2 wt % in still another embodiment.
The at least one solvent compound, component (c), of the present invention can include one or more compounds including, for example, any conventional carrier solvent such as ethyl acetate, methyl ethyl ketone, dioxolane, propyl acetate, toluene, and mixtures thereof. In one preferred embodiment, the solvent compound useful in the present invention can be ethyl acetate, methyl ethyl ketone, and mixtures thereof.
The amount of the solvent compound used to make isocyanate-reactive co-reactant, component (b), of the present invention process is, for example, from 10 wt % to 90 wt % in one embodiment, from 30 wt % to 85 wt % in another embodiment and from 50 wt % to 80 wt % in still another embodiment.
In some embodiments, the adhesive composition of the present invention can include one or more optional additives including but are not limited to, for example, tackifiers, catalysts plasticizers, rheology modifiers, adhesion promoters, antioxidants, fillers, colorants, surfactants, solvents, and combinations of two or more thereof.
The amount of the optional components useful in the adhesive composition can be, for example, from 0 wt % to 3 wt % in one embodiment, from 0 wt % to 2 wt % in another embodiment and from 0.01 wt % to 1 wt % in still another embodiment.
In general, the process of making the laminating adhesive composition includes the steps of: (I) melting a crystalline polycarbonate diol at a temperature of from 50° C. to 70° C.; (II) pouring the melted diol into a reactor, where the reactor has been preheated at a temperature of from 50° C. to 60° C.; (II) loading the solvent and any other optional additives into the reactor; (IV) mixing all components in the reactor with agitation until a uniformly mixed, fully clear solution is formed; and (V) removing the resulting the fully clear solution from the reactor.
A multi-layer laminate product can be formed including a layer of the solvent-based polyurethane adhesive composition based on a crystalline polycarbonate of the present invention. Any number of layers can be used to form the laminate product. In one preferred embodiment, the laminate is formed by the steps of: applying the adhesive composition to at least one of two substrate layers (e.g., the substrates can be made of the same material or of different materials); combining the substrates together such that the adhesive composition is disposed as a layer between the surfaces of the two substrates; and then curing the adhesive composition to form a bonding layer between the two substrates. In general, each of the two substrates can include, for example, two separate polymer films. As used herein, a “film” is any layer structure that is 0.5 mm or less in one dimension of the layer structure; and is 1 cm or more in both of the other two dimensions of the layer structure. A “polymer film” is a film that is made of a polymer or mixture of polymers. The composition of a polymer film is, typically, 80 percent by weight or more of one or more polymers.
Suitable substrates used to form the laminate structure include films such as paper, woven and nonwoven fabric, polymer films, metal-coated (metallized) polymer films, and combinations thereof. The substrates are layered to form a laminate structure, with an adhesive composition according to the present invention adhering one or more of the substrates together.
In a preferred embodiment, the multi-layer laminate product prepared using the adhesive composition of the present invention includes: (A) at least a first layer; (B) at least a second layer; and (C) at least one layer of the adhesive composition disposed inbetween the first layer and the second layer; wherein the adhesive is cured to bond the first layer to the second layer.
In one general embodiment, the multi-layer laminate product can be two or more film substrates or film layers combined together with the adhesive composition. In some embodiments, the laminate product is a laminate film structure including a first film layer, a second film layer, and a barrier adhesive layer disposed intermediate the first film layer and the second film layer. For example, in a preferred embodiment, the multi-layer laminate product can be made of three layers including the first film layer (or outer layer), the second film layer (or inner layer) and a bonding layer comprising the adhesive composition disposed inbetween the first and second layers.
The 3-layer laminate product of the present invention can have a layered structure of A/B/A wherein A represents the first and second layers being of the same material and wherein B represents the bonding layer of adhesive composition. Although a 3-layer laminate film product is referenced herein, the present invention includes a multi-layer laminate member with any number of film layers provided at least one layer of the multi-layer film member is the bonding layer of adhesive composition, where the bonding layer has the proper gas barrier properties. As aforementioned, the structure of the multi-layer film member can be A/B/A wherein both layers represented by A is made of the same polymer material; or the structure of the multi-layer film member can be A/B/C wherein C represents a film layer than is made of a different material than the layer of A. Or, the structure of the multi-layer film member can be any combination of A, B, and C layers which are apparent to one skilled in the art of laminate making.
The first layer of the present invention laminate product can be made of one or more materials, including, for example, polyethylene, polypropylene, polyethylene terephthalate, polyamide, polystyrene, cycloolefin copolymer, polyvinyl chloride, styrene butadiene, and the like. In one preferred embodiment, the material of the first layer useful in the present invention can be polypropylene, polyethylene, and combinations thereof. Exemplary of some of the commercial materials useful in the first layer of the present invention can include, for example, biaxial oriented polypropylene (available from FILMTECH, INC.); and polyethylene (available from Berry Plastics); and mixtures thereof. In another preferred embodiment, the first film layer can be made of, for example, polypropylene having a density of from 0.89 g/cc to 0.92 g/cc.
The thickness of the first layer used in the present invention laminate product is, for example, from 10 μm to 200 μm in one embodiment, from 15 μm to 150 μm in another embodiment and from 20 μm to 125 μm in still another embodiment.
As aforementioned, the second layer of the present invention laminate product can be made of the same material as the first layer which has the advantage of being more easily recyclable. In another embodiment, the second layer can be made of one or more materials different from the first layer.
When the second layer of the laminate product is made of a different polymer from the first layer, the second layer can include, for example, polyethylene, polypropylene, polyethylene terephthalate, polyamide, polystyrene, cycloolefin copolymer, polyvinyl chloride, styrene butadiene, and mixtures thereof. In one preferred embodiment, the material of the second layer useful in the present invention can be polyethylene, polypropylene, and mixtures thereof. Exemplary of some of the commercial materials useful in the second layer of the present invention can include, for example, polyethylene (available from Berry Plastics); and biaxial oriented polypropylene (available from FILMTECH, INC.); and mixtures thereof. In another preferred embodiment, the second film layer, when different from the first layer, can be made of, for example, polyethylene having a density of from 0.915 g/cc to 0.967 g/cc.
The thickness of the second layer used in the present invention film is, for example, from 10 μm to 200 μm in one embodiment, from 15 μm to 150 μm in another embodiment and from 20 μm to 125 μm in still another embodiment.
In general, one process for producing the multi-layer laminate product described above includes the steps of:
(I) applying the adhesive composition of the present invention to at least a portion of the surface of the first layer and/or the second layer;
(II) contacting the first layer and the second layer such that the adhesive is disposed inbetween the first layer and the second layer; and
(III) curing the adhesive to form a multi-layer laminate product comprising the first layer bonded to the second layer via the cured adhesive.
The laminate film structure of the present invention includes films made from polymers bonded together using a barrier adhesive composition in place of a standard adhesive composition, while the laminate film structure of the present invention still achieves similar or enhanced barrier properties. One of the advantageous properties exhibited by the laminate product made by the above process of the present invention can include, for example, a laminate having an improved (i.e., a reduced) oxygen transmission rate (OTR). In some embodiments, the laminate film structure has an OTR not greater than 750 cubic centimeters of oxygen per [square meter-day] abbreviated as “ccO2/m2/day” and measured according to ASTM Method D3985.
Because a laminate film structure can be designed with various layer materials, number of layers, film thicknesses and other properties, the OTR of a particular laminate structure will depend on, for example, the various properties of the first and second layers. As an illustration, and not to be limited thereby, the OTR of the laminate structure of the present invention is generally 15% less than a laminate using a standard adhesive composition in one embodiment, 25% less than a laminate using a standard adhesive composition in another embodiment, and 50% less than a laminate using a standard adhesive composition in still another embodiment. In yet another embodiment, the OTR of the laminate structure of the present invention is from 10% to 90% less than a laminate using a standard adhesive composition.
The laminate prepared as described above can be used, for example, in flexible packaging applications; and in home and personal care applications. In one preferred embodiment, the laminate is used to make a multi-layer laminate structure product or article such as a package, pouch or container for packaging food. In a preferred embodiment, the laminate is made of two layers of polymeric film with an adhesive layer disposed inbetween the two film layers bonding the two polymer films together. The process of making an article such as a food packaging article can be carried out by those skilled in the art of food packaging manufacturing.
As described above, there is a reduction in the permeability of oxygen through the laminate structures by using the barrier adhesive layer of the present invention in place of standard adhesives; and therefore, the article which is made using the laminate described above will have the same advantageous gas barrier properties such as an improved (i.e., a reduced) OTR as exhibited by the laminate described above.
In addition, a multi-layer laminate having an ABA structure can advantageously be a simple, readily manufacturable structure and can also beneficially be recyclable such that the food packaging made from the laminate is environmentally friendly.
The following examples are presented to further illustrate the present invention in detail but are not to be construed as limiting the scope of the claims. Unless otherwise indicated, all parts and percentages are by weight.
Various raw materials or ingredients used in the Inventive Examples (Inv. Ex.) and the Comparative Examples (Comp. Ex.) are explained as follows:
MOR-FREE™ C33 is an aliphatic based isocyanate and is available from The Dow Chemical Company (Dow).
ADCOTE™ 577 is an isocyanate-terminated compound and is available from Dow.
ADCOTE™ 577B is a hydroxyl-terminated compound and is available from Dow.
ETERNACOLL®UH-100 is a 1,6-hexanediol based crystalline polycarbonate diol having a molecular weight (Mw) of 1,000 and a melting point of about 45° C.; and is available from UBE Industries Company (UBE).
ETERNACOLL®UH-200 is a 1,6-hexanediol based crystalline polycarbonate diol having a Mw of 2,000 and a melting point of about 50° C.; and is available from UBE.
ETERNACOLL®PH-100 is a non-crystalline co-polycarbonate diol having a Mw of 1,000 wherein 1,4-cyclohexane dimethanol and 1,6 hexanediol are applied as co-polycarbonate diol component; and is available from UBE.
MODAFLOW® Resin is an acrylic copolymer and is available from Allnex Inc.
“BOPP” stands for biaxial-oriented polypropylene. BOPP is a film having a thickness of 20 μm and is available from Filmtech Inc.
A 90° T-peel test was done on laminate samples consisting of two films, a primary film and a secondary film adhered together with an adhesive. The laminate samples were cut to 15 mm wide strips and each of the samples were pulled on a Thwing Albert™ QC-3A peel tester equipped with a 50 N loading cell. The laminate samples were pulled with the peel tester at a rate of 4 in/min (10 cm/min) on the 15 mm strips. When the two films in the laminate separated (peeled), the average of the force during the pull was recorded. If one of the films stretched or broke, the maximum force or force at break was recorded. The final value for the laminate sample is the average value of three separate sample strips tested. The failure mode (FM) or mode of failure (MOF) was recorded as follows: AS (Adhesive Split) or cohesive failure which indicates that adhesive is found on both the primary and the secondary film.
An oxygen transmission rate (OTR) of the formed laminate was measured using a MOCON OXTRAN 2/21 under ASTM method D3985 (“Standard Test Method for Oxygen Gas Transmission Rate through a Plastic Film and Sheeting Using a Coulometric Sensor”). The OTR data is reported in the standard unit “cc/(m2-day)”. The conditions used for testing to obtain OTR measurements were 23° C. and 85% relative humidity (RH).
The co-reactants (CR) described in Table I are prepared using a crystalline polycarbonate diol compound or non-crystalline polycarbonate diol compound. The polycarbonate diol is first melted in an oven at 60° C.; and then the melted crystalline or non-crystalline polycarbonate diol compound is mixed with ethyl acetate and an acrylic polymer at 60° C. for 1 hr to form the isocyanate reactive component composition.
The adhesive formulations described in Table II are prepared by mixing the components listed in Table V under the following conditions:
The pertinent ingredients for preparing the adhesive formulations, the isocyanate-reactive component, and the isocyanate component are described in Table II. Using the adhesive of Inventive Example 1 as an illustration for an adhesive formulation sample preparation, about 2,541 g of isocyanate-reactive component (Component B), about 459 g of isocyanate component (Component A) are loaded into a plastic container. The materials are mixed using a mechanical mixer at room temperature (about 25° C.) for 30 min to obtain the formulated adhesive of Inventive Example 1.
Table II describes the adhesive formulations of selected examples wherein all the adhesives have the same amount of excess isocyanates.
A polyurethane adhesive is prepared as described above using the general procedure for preparing an adhesive formulation. The adhesive is first coated on a primary substrate via gravure cylinder. The coated film is then passed through a three zoned oven. The coated film is then nipped to another substrate under a heated steel roll with a temperature of 90° C., and a nip pressure set to 40 pounds per square inch (275.8 kPa). The laminated structure is passed through a final chill roll at a chill roll temperature of 17° C. The resultant laminate is then placed in a temperature control room to cure at 23° C. for 7 days and 50% RH.
Coated laminates were produced using the polyurethane adhesive compositions of Inv. Ex. 1-3 described above in Table II and using the general procedure for preparing a coated laminate as described above. Each of the resultant laminates of Inv. Ex. 4-6 had an adhesive coating weight of 3.5 g/m2.
A coated laminate was produced using the polyurethane adhesive composition of Comp. Ex. A described above in Table II and using the general procedure for preparing a coated laminate as described above. The resultant laminate of Comp. Ex. A had an adhesive coating weight of 3.5 g/m2.
The same general procedure for preparing a coated laminate as described above was used in this Comp. Ex. B except that a polyurethane adhesive comprising about 55 wt % ADCOTE™ 577, 4.9 wt % ADCOTE™ 577B and 40.1 wt % ethyl acetate was used. And in this Comp. Ex. B, after the laminated structure is passed through a final chill roll at a chill roll temperature of 17° C., the laminate was placed in a temperature control room to cure at 23° C. for 7 days and 50% RH. The laminate had an adhesive coating weight of 3.5 g/m2.
From the data described in the following Table III, it can be seen that the laminates of Inv. Ex. 4, 5 and 6 coated with the adhesive formulations of Inv. Ex. 1, 2 and 3, respectively, containing a crystalline polycarbonate showed improved OTR barrier performance versus the laminates of Comp. Ex. C and Comp. Ex. D coated with an adhesive formulation containing a non-crystalline polycarbonate backbone.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/028749 | 4/23/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63033861 | Jun 2020 | US |
