Solvent-free polyurethane adhesive compositions and uses thereof

Abstract

A solvent-free polyurethane adhesive composition comprising: (A) at least one isocyanate group-containing component comprising at least one isocyanate-terminated polyurethane prepolymer obtained by reacting a polyol mixture with a stoichiometric excess of at least one polyisocyanate, the present invention relates to a composition comprising a polyol mixture comprising: (a) at least one polyester polyol obtained by reacting a reactant mixture comprising (i) at least one polycarboxylic acid selected from the group consisting of at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid, (ii) neopentyl glycol, and (iii) at least one polyol having a weight average molecular weight of 50 to 300 g / mol other than neopentyl glycol; and (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol; and (B) at least one hydroxyl group-containing component; wherein the isocyanate group-containing component (A) has an NCO content of greater than 10% by weight to less than 14% by weight.

Description

Technical Field

[0001] The present invention relates to a solvent-free polyurethane adhesive composition and its use. In particular, the present invention relates to a solvent-free polyurethane adhesive composition for laminating PET and aluminum foil in food packaging. Background Art

[0002] Film-to-film and film-to-foil laminates are used in the packaging of various food products and other industrial products. Adhesives and coatings are used in the manufacture of these composite structures because it is generally difficult to achieve satisfactory bonding of films of different compositions using coextrusion or thermal welding techniques. This type of laminate needs to have many key performance characteristics so that the packaged goods can be safely placed, transported and stored until they are used by the customer. During the multiple stages of packaging, the laminate is subjected to various treatments, such as printing, bagging, bag making, filling, boxing, transportation, etc. For more than 20 years, people have been using formulations based on polyurethanes produced mainly by the reaction of polyols and polyisocyanates. These products are mainly solvent solutions of polyesters and or polyether polyols appropriately reacted with aromatic isocyanates such as MDI (diphenylmethane diisocyanate), TDI (toluene diisocyanate) and many reaction products of diisocyanates. Due to the increasing environmental awareness, such solvent solutions are replaced by solvent-free polyurethanes in most applications. Although some water-based laminating adhesives are known, most are provided in the form of 100% solid systems. These systems are essentially similar to solvent-borne products, but they contain large amounts of free monomeric isocyanates. Their volatility, the health effects of these isocyanates and their reaction products with air moisture leading to the formation of aromatic diamines have become a cause of concern, especially in food packaging. Almost all adhesives and most coatings used in industry are based on polyurethanes. When films that are considered to be high barrier materials (which means that they do not allow gases to pass freely through them) are to be laminated, such adhesives containing free isocyanates can cause appearance problems. Trace amounts of moisture present in the film surface react with isocyanates in a well-known manner to form carbamic acid. This unstable acid releases carbon dioxide gas. Due to the impermeability of the film, the carbon dioxide is trapped as bubbles, leading to appearance problems.

[0003] US2019 / 0127616 A1 discloses a solvent-free adhesive comprising an isocyanate component and a polyol component, wherein the isocyanate component comprises at least one isocyanate prepolymer, the isocyanate prepolymer is the reaction product of reactants comprising at least one isocyanate, at least one polyol and a branched alkane diol; the polyol component comprises at least one polyol and a branched alkane diol. The branched alkane diol may comprise a single-side alkyl chain, such as 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, and combinations thereof. After being immersed in water during boiling in the bag, the bag formed by the laminated film has a good appearance and no tunneling phenomenon.

[0004] EP3947588 A1 discloses a solvent-free adhesive composition comprising (A) a solvent-free adhesive having a composition consisting of —R2—(O—R1—O) n — isocyanate prepolymer of a side chain represented by R3 and (B) an isocyanate reactive component, and exhibits improved bonding strength, heat seal strength, adhesive COF properties and optical appearance on PET ink / MPET lamination.

[0005] None of the above prior art discloses a solvent-free adhesive composition that exhibits a desirable low viscosity and a satisfactory optical appearance, especially on PET and aluminum foil. Therefore, there is a need in the art for a solvent-free polyurethane adhesive composition that has a desirable low viscosity and exhibits a satisfactory optical appearance when laminated on a film or foil, especially on PET / aluminum foil. Summary of the invention

[0006] Disclosed herein is a solvent-free polyurethane adhesive composition comprising:

[0007] (A) at least one isocyanate group-containing component comprising at least one isocyanate-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising:

[0008] (a) at least one polyester polyol obtained by reacting a reactant mixture comprising:

[0009] (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid,

[0010] (ii) neopentyl glycol, and

[0011] (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and

[0012] (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol, and

[0013] (B) at least one hydroxyl-containing component;

[0014] The NCO content of the isocyanate group-containing component (A) is greater than 10% by weight and less than 14% by weight.

[0015] Also disclosed herein is a laminate comprising a first layer, a second layer and an adhesive layer sandwiched therebetween, wherein the first and second layers are independently selected from films made of PET (polyethylene terephthalate), PP (polypropylene), OPP (oriented polypropylene), CPP (cast polypropylene), BOPP (biaxially oriented polypropylene), PE (polyethylene), aluminum foil, PA (polyamide), VMPET (vacuum metallized polyethylene terephthalate) and VMCPP (vacuum metallized cast polypropylene), preferably a film made of PET (polyethylene terephthalate) and aluminum foil, and the adhesive layer is formed by curing the adhesive composition according to the present invention.

[0016] Also disclosed herein are food bags formed from the laminates of the present invention.

[0017] Additionally disclosed herein is the use of a solvent-free polyurethane adhesive composition according to the invention or a laminate according to the invention for producing food packaging.

[0018] Other features and aspects of the subject matter are set forth in greater detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A photograph showing the optical appearance of the solvent-free polyurethane adhesive composition according to Example 1 after being laminated to a PET film and an aluminum foil is shown.

[0020] Figure 2 A photograph of the optical appearance of the solvent-free polyurethane adhesive composition according to Comparative Example 1 after being laminated to a PET film and an aluminum foil is shown.

[0021] Figure 3 A photograph showing the optical appearance of the solvent-free polyurethane adhesive composition according to Example 3 after being laminated to a PET film and an aluminum foil is shown. DETAILED DESCRIPTION

[0022] Those of ordinary skill in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0023] Unless otherwise specified, in the context of the present invention, the terms used should be interpreted according to the following definitions.

[0024] As used herein, the terms "a," "an," "said," and "the" include both singular and plural referents unless otherwise specified.

[0025] As used herein, the term "composition" refers to a mixture of materials which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0026] As used herein, the terms "comprising" and "containing" are synonymous with "including" or "containing", are inclusive or open-ended, and do not exclude additional, unrecited members, elements, or method steps.

[0027] The term "at least one" or "one or more" used herein to define a component refers to the type of the component, rather than the absolute number of molecules. For example, "one or more polyols" refers to a type of polyol or a mixture of multiple different polyols.

[0028] The term "room temperature" as used herein refers to a temperature of about 20°C to about 25°C, preferably about 25°C.

[0029] The term "polyol" as used herein is understood to mean a molecule carrying two or more hydroxyl groups, whether or not the molecule contains other functional groups. However, the polyols that can be used in the present invention preferably contain only one OH group, or if other functional groups are present, these other functional groups are at least unreactive towards isocyanates under the conditions of the present invention.

[0030] Unless otherwise specified, recitations of numerical endpoints include all numbers and fractions subsumed within the corresponding range, as well as the recited endpoint.

[0031] Molecular weights refer to weight-average molecular weight (Mw), unless otherwise specified. All molecular weight data refer to values ​​obtained by gel permeation chromatography (GPC), for example according to DIN 55672, unless otherwise specified.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0033] According to a first aspect of the present invention, disclosed herein is a solvent-free polyurethane adhesive composition comprising:

[0034] (A) at least one isocyanate group-containing component comprising at least one isocyanate-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising:

[0035] (a) at least one polyester polyol obtained by reacting a reactant mixture comprising:

[0036] (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid,

[0037] (ii) neopentyl glycol, and

[0038] (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and

[0039] (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol, and

[0040] (B) at least one hydroxyl-containing component;

[0041] The NCO content of the isocyanate group-containing component (A) is greater than 10% by weight and less than 14% by weight.

[0042] (A) Components containing isocyanate groups

[0043] According to the invention, the at least one isocyanate group (NCO)-containing component (A) comprises at least one isocyanate group (NCO)-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising:

[0044] (a) at least one polyester polyol obtained by reacting a reactant mixture comprising:

[0045] (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid,

[0046] (ii) neopentyl glycol, and

[0047] (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and

[0048] (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol.

[0049] Preferably, the weight average molecular weight (Mw) of the NCO-terminated polyurethane prepolymer useful in the present invention is in the range of 200 to 100,000 g / mol, more preferably in the range of 500 to 5,000 g / mol.

[0050] Preferably, the at least one NCO-terminated polyurethane prepolymer comprises 5 to 95 wt%, preferably 30 to 60 wt%, based on the total weight of the adhesive composition.

[0051] (a) Polyester polyol

[0052] According to the present invention, suitable polyester polyols in the present invention can be obtained by reacting a reactant mixture comprising: (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid, (ii) neopentyl glycol, and (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol. By selecting neopentyl glycol to prepare the polyester polyol, it is possible to produce a polyurethane adhesive composition having a good optical appearance when laminated and cured.

[0053] In a preferred embodiment, the reactant mixture comprises at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid.

[0054] Specific examples of suitable aliphatic dicarboxylic acids as component (i) may be C2-C36 aliphatic dicarboxylic acids selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, dimer acid, and combinations thereof, preferably selected from adipic acid, sebacic acid, succinic acid, their corresponding polycarboxylic acid anhydrides, and combinations thereof.

[0055] Specific examples of suitable aromatic dicarboxylic acids as component (i) may be C8-20 aromatic dicarboxylic acids selected from isophthalic acid, terephthalic acid, biphenylcarboxylic acid and 2,6-naphthalene dicarboxylic acid, and their corresponding polycarboxylic acid anhydrides, and combinations thereof, preferably selected from isophthalic acid, terephthalic acid, their corresponding polycarboxylic acid anhydrides, and combinations thereof.

[0056] Specific examples of suitable polyols other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol as component (iii) can be selected from ethylene glycol, diethylene glycol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, 1,2-propanediol, dipropylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, 2-butyl-2-ethylpropanediol, pentaerythritol, polytetramethylene ether glycol and combinations thereof, preferably selected from ethylene glycol, diethylene glycol, 1,2-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol and combinations thereof.

[0057] Polyester polyols prepared by polycondensation of neopentyl glycol (ii) according to the invention and at least one polyol (iii) other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol with a stoichiometric excess of at least one polycarboxylic acid (i) according to the invention selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid can be used. The above polycarboxylic acids can be used alone or as a mixture of two or more thereof.

[0058] The method for preparing suitable polyester polyols that can be used in the present invention comprises the following steps: (i) mixing one or more polycarboxylic acids, neopentyl glycol and one or more other polyols described above at a temperature of 120 to 250° C. under the protection of a nitrogen stream for 6 to 12 hours to ensure that polycondensation occurs; (ii) applying a vacuum of 50 to 900 mBar for 1 to 12 hours in the second half of the reaction to improve the molecular weight of the obtained polyester polyol.

[0059] Preferably, the polyester polyol useful in the present invention has a weight average molecular weight (Mw) of 450 to 2,000 g / mol, more preferably in the range of 800 to 1500 g / mol.

[0060] In some embodiments, the polyester polyols can be modified by a vegetable oil selected from castor oil, soybean oil, palm oil, coconut oil and combinations thereof. When a polyester polyol modified with a vegetable oil is used, the amount of the vegetable oil is preferably no more than 5% by weight of the adhesive composition. The preferred adhesive composition of the present invention does not contain any vegetable oil.

[0061] Commercially available products can also be used in the present invention. Examples include: PES 5622, PES9000 from Henkel, CP-2070 from Nanjing CSD, and ES-980 from SKC.

[0062] Particularly preferably, the polyester polyol used to prepare component (A) may be present in an amount of 5% to 30% by weight, and more preferably 10% to 25% by weight, based on the weight of component (A).

[0063] (b) Polyether polyol

[0064] According to the present invention, at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol is included to prepare component (A) used in the composition of the present invention.

[0065] The polyether polyols used to prepare component (A) in the present invention are well known to those skilled in the art. These polyether polyols are obtained by copolymerizing at least one compound of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, etc. with at least one compound having an average of at least two active hydrogen atoms in one molecule (e.g., the polyols listed above, which include ethylene glycol, propylene glycol, dipropylene glycol, glycerol, and combinations thereof). Other suitable polyvalent compounds include sucrose, ethylenediamine, propylenediamine, triethanolamine, 1,2-propanedithiol, and combinations thereof.

[0066] Preferred polyether polyols for preparing component (A) can be selected from polytetramethylene ether glycol, poly(oxypropylene) glycol, polyethylene oxide, polybutylene oxide, and ethylene oxide-terminated forms of any of the above substances, and combinations thereof. The most preferred polyether polyols are polytetramethylene ether glycol, poly(oxypropylene) glycol, ethylene oxide-terminated poly(oxypropylene) glycol, and combinations thereof.

[0067] In a preferred embodiment, the average molecular weight (Mw) of the polyether polyol is from 450 to 2,000 g / mol.

[0068] Commercially available products can be used in the present invention. Examples thereof include: DP 450, DP 1000M and DP 2000M from Kukdo Chemical Company.

[0069] Particularly preferably, the polyether polyol may be present in an amount of 10% to 50% by weight, and more preferably 20% to 40% by weight, based on the weight of component (A).

[0070] Polyisocyanate

[0071] According to the invention, component (A) of the invention comprises at least one NCO-terminated polyurethane prepolymer which is obtained by reacting the above-described polyol mixture with a stoichiometric excess of at least one polyisocyanate.

[0072] As used herein, the term "polyisocyanate" is understood to preferably have 2 to 4 isocyanate groups per molecule. Preferably, the polyisocyanate is a diisocyanate, including aliphatic, alicyclic, aromatic diisocyanates.

[0073] In one embodiment, the aromatic diisocyanate may be selected from 2,2'-methylene diphenyl diisocyanate (MDI), 4,4'-methylene diphenyl diisocyanate, 2,4'-methylene diphenyl diisocyanate, 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate, 1,3-phenylene diisocyanate (PDI), 1,4-phenylene diisocyanate, 1,4-naphthylene diisocyanate (NDI), 1,5-naphthylene diisocyanate, tetramethylxylene diisocyanate (TMXDI), 4,4'-dibenzyl diisocyanate, xylene diisocyanate (XDI), and combinations thereof.

[0074] In one embodiment, the aliphatic isocyanate may be selected from butane-1,4-diisocyanate, 1,6-hexamethylene diisocyanate (HMDI), 1,6-diisocyanato-2,2,4-trimethylhexane, 1,12-diisocyanato-dodecane, and combinations thereof.

[0075] In one embodiment, the alicyclic isocyanate may be selected from isophorone diisocyanate (IPDI), 4,4-dicyclohexylmethane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-diisocyanatocyclohexane, and combinations thereof.

[0076] Preferably, the polyisocyanate may be selected from 2,2'-methylene diphenyl diisocyanate, 4,4'-methylene diphenyl diisocyanate, 2,4'-methylene diphenyl diisocyanate, 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and combinations thereof. More preferably, MDI is used as the polyisocyanate.

[0077] Commercially available products can be used in the present invention. Examples thereof include: Desmodur 44CFUSED, Desmodur 0118I and Desmodur 44M from Covestro, Vannate MDI 100F from Wanhua Chemicals, and Supresec 1809 from HUNTSMAN.

[0078] Particularly preferably, the polyisocyanate may be present in an amount of 40% to 85% by weight, and more preferably 55% to 80% by weight, based on the weight of component (A).

[0079] The stoichiometric excess of the polyisocyanate and polyol mixture described above is in the NCO-containing component (A) - with respect to the molar ratio of -NCO groups to -OH groups - in particular greater than 1:1 to 50:1, preferably 2:1 to 10:1. Due to the excess isocyanate used, the NCO-terminated polyurethane prepolymer usually contains a certain amount of isocyanate monomers. In order to achieve the desired effect of the present invention, the NCO content of the NCO-containing component (A) is greater than 10% by weight to less than 14% by weight. If the NCO content is not within the claimed range, the optical appearance of the laminate formed by the adhesive composition will show orange peel, small spots or bubbles.

[0080] The NCO content based on the isocyanate-containing component (A) can be determined in accordance with ISO 14896 / 3 using acetone as solvent.

[0081] (B) Hydroxyl-containing components

[0082] According to the present invention, component (B) of the solvent-free polyurethane adhesive composition may be at least one hydroxyl (OH)-containing component.

[0083] Preferably, the hydroxyl value of the OH-containing component (B) in the present invention is in the range of 10 to 1500 mgKOH / g, preferably in the range of 56 to 560 mgKOH / g.

[0084] The term "hydroxyl value" used herein is defined as the number of milligrams of potassium hydroxide required to neutralize the acetic acid taken up when acetylation is performed on 1 g of a hydroxyl component, expressed in milligrams of potassium hydroxide (KOH) mass units, which is equivalent to the hydroxyl content of 1 g of the hydroxyl component. In the present invention, the hydroxyl value is determined according to DIN 53240-2.

[0085] Preferably, the average hydroxyl functionality of the OH-containing component (B) in the present invention is from 2 to 5, preferably from 2 to 4.

[0086] The viscosity of the OH-containing component (B) is not particularly limited. From the viewpoint of final use, the viscosity of the component (B) is preferably in the range of 50 to 20,000 mPa.s at 25°C, more preferably in the range of 500 to 10,000 mPa.s at 25°C.

[0087] Typically, the OH-containing component (B) can be any and all commonly used polyols, such as polyester polyols, polyether polyols, polyester ether polyols, polycarbonate polyols, and combinations thereof. In some embodiments, the polyols that can be used to prepare component (B) include the polyol mixtures used in the preparation of the NCO-terminated polyurethane prepolymers in component (A).

[0088] Particularly preferably, the OH-containing component (B) may be present in an amount of 5 to 95 wt %, and more preferably 10 to 56 wt %, based on the total weight of the adhesive composition.

[0089] additive

[0090] Optionally, conventional additives may be included in one or both of components (A) and (B) independently of each other without impairing the purpose of the present invention. Such additives may be those commonly used in the art, such as fillers, colorants, defoamers, etc.

[0091] Examples of fillers are selected from calcium carbonate, titanium dioxide, carbon black, talc, china clay, mica powder, diatomaceous earth, alumina, and combinations thereof.

[0092] Examples of colorants include pigments, which may be selected from metal oxide pigments, titanium dioxide, optionally surface treated zirconium oxide or cerium oxide, zinc oxide, iron oxide (black, yellow or red), chromium oxide, manganese, and combinations thereof.

[0093] Particularly preferably, one or more additives may be present in an amount of 0 to 5 wt %, and preferably 0.01 wt % to 5 wt %, based on the total weight of the adhesive composition.

[0094] Mixing ratio of components (A) and (B)

[0095] In some embodiments, the mixing ratio of the NCO-containing component (A) to the OH-containing component (B) is 5:100 to 19:1 parts by weight, preferably 50:100 to 200:100 parts by weight.

[0096] Adhesive composition

[0097] In a particularly preferred embodiment, the solvent-free polyurethane adhesive composition comprises, based on the total weight of the adhesive composition:

[0098] (A) 5 to 95% by weight, preferably 30 to 60% by weight, of at least one NCO-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising:

[0099] (a) at least one polyester polyol obtained by reacting a reactant mixture comprising:

[0100] (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid,

[0101] (ii) neopentyl glycol, and

[0102] (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and

[0103] (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol, and

[0104] (B) 5 to 95% by weight, preferably (B) 10 to 56% by weight, of at least one OH-containing component;

[0105] The NCO content of the NCO-containing component (A) is greater than 10 wt % and less than 14 wt %.

[0106] In a particularly preferred embodiment, the at least one NCO-containing component (A) comprises at least one NCO-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising:

[0107] (a) 5 to 30 wt. %, and more preferably 10 to 25 wt. %, of at least one polyester polyol obtained by reacting a reactant mixture comprising: (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid, (ii) neopentyl glycol, and (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and

[0108] (b) 10 to 50 wt. %, and more preferably 20 to 40 wt. %, of at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol, all weight proportions being based on the weight of component (A); wherein the NCO content of the NCO-containing component (A) is greater than 10 wt. % to less than 14 wt. %.

[0109] In some embodiments, the NCO-containing component (A) of the present invention can be prepared by the following steps:

[0110] (i) adding one or more polyisocyanates into a reactor at 60° C. under the protection of nitrogen flow;

[0111] (ii) introducing a polyol mixture into the reactor and controlling the water content in the reactor to be less than 300 ppm, and then gradually raising the temperature to as high as 80° C. and maintaining it for 2 to 3 hours; and

[0112] (iii) When the NCO content reaches the desired content of the present invention, the produced NCO-containing component (A) can be charged into a container at 60°C under the protection of nitrogen flow.

[0113] In some embodiments, the OH-containing component (B) can be directly obtained from commercially available products described herein. In other embodiments, the OH-containing component (B) can be obtained by mixing useful polyols described herein by conventional methods.

[0114] Components (A) and (B) of the present invention may be mixed before use, and the uncured adhesive composition may then be applied to at least one of the flexible substrates (eg, films, foils) to be bonded, and the flexible substrates may then be laminated together, followed by curing.

[0115] The instruments used for these mixing, stirring, dispersing, etc. are not particularly limited. Automatic mortar, Henschel mixer, three-roll mill, ball mill, planetary mixer, bead mill, etc. can be used, which are equipped with a stirrer and a heater. In addition, a suitable combination of these instruments can be used. The preparation method of the solvent-free polyurethane adhesive composition is not particularly limited, as long as the composition in which the above components are uniformly mixed.

[0116] Laminate, food bag and use

[0117] In some embodiments, the solvent-free polyurethane adhesive composition of the present invention may be cured at 25° C. to 65° C., preferably room temperature, for 1 to 7 days.

[0118] As will be appreciated, the time and temperature cure profile of each solvent-free polyurethane adhesive composition will vary, and different compositions may be designed to provide a cure profile suitable for a particular industrial manufacturing process.

[0119] In another aspect of the present invention, provided herein is a laminate comprising a first layer, a second layer and an adhesive layer sandwiched therebetween, wherein the first and second layers are independently selected from films made of PET (polyethylene terephthalate), PP (polypropylene), OPP (oriented polypropylene), CPP (cast polypropylene), BOPP (biaxially oriented polypropylene), PE (polyethylene), aluminum foil, PA (polyamide), VMPET (vacuum metallized polyethylene terephthalate) and VMCPP (vacuum metallized cast polypropylene), preferably a film made of PET and aluminum foil, and the adhesive layer is formed by curing the adhesive composition according to the present invention.

[0120] A "layer" is any substrate or film having one dimension of 0.5 mm or less and two other dimensions of 1 cm or greater that is flexible (eg, a flexible layer, ie, the layer can be bent using no more than two hands).

[0121] The first layer and / or the second layer may be a single material and a single layer, or may include multiple layers of the same or different materials as described herein.

[0122] In a particularly preferred embodiment, the solvent-free polyurethane adhesive composition of the present invention is used for laminating PET (polyethylene terephthalate) and aluminum foil.

[0123] Typically, the size of the laminate may be 10 to 20,000 meters, 10 to 15,000 meters, and preferably 20 to 8,000 meters in length and 0.1 μm to 0.5 mm, preferably 1 μm to 10 μm in thickness. The amount of the adhesive composition is typically about 1 to 5 g.

[0124] A method for forming a laminate using the solvent-free polyurethane adhesive composition of the present invention is disclosed herein. In some embodiments, the solvent-free polyurethane adhesive composition is first heated to a temperature lower than 45° C. and then applied to the surface of the first layer. Then, the surface of the second layer is contacted with the layer of the adhesive composition to form an uncured laminate. The adhesive composition can be applied by a conventional solvent-free machine (e.g., Super Combi 3000 from Nordmeccanic). The adhesive composition can then be cured or cured. Pressure can be applied to the uncured laminate, for example, by passing through a nip roller, which can be heated or not heated. The uncured laminate can be heated to accelerate the curing reaction.

[0125] The method of the present disclosure can be implemented continuously or discontinuously. An example of a continuous process is a roll-to-roll process. The length of the layer is typically 10 to 20,000 meters, 10 to 15,000 meters, and preferably 20 to 8,000 meters, and the layer is typically conveyed at a speed in the range of 0.1 to 60 m / min, preferably 3 to 45 m / min, and more preferably 5 to 15 m / min.

[0126] The solvent-free polyurethane adhesive composition of the present invention can be applied to the layer using any suitable application method, including, for example, automatic fine line dispensing, jet dispensing, slot die coating, roller coating, gravure coating, transfer coating, pattern coating, screen printing, spray coating, filament coating, by extrusion, air knife, drag blade, brush coating, dipping, doctor blade, gravure coating, rotogravure coating, and combinations thereof. The solvent-free polyurethane adhesive composition can be applied as a continuous or discontinuous coating, in a single layer or multiple layers, and combinations thereof.

[0127] The laminates disclosed herein may be cut or otherwise formed to have a shape suitable for any desired purpose, such as packaging material.

[0128] In yet another aspect of the present invention, provided herein is a food bag formed from the laminate of the present invention.

[0129] Examples of food products that may be contained in such packages include meats, cheeses, cereals, nuts, juices, sauces, etc.

[0130] The solvent-free polyurethane adhesive compositions and laminates described above can be used to make food packaging. Such food packaging can be formed using techniques known to those skilled in the art based on the teachings herein and based on the specific use (e.g., type of food, amount of food, etc.) for the packaging.

[0131] Example

[0132] The following examples are intended to help those skilled in the art better understand and practice the present invention. The scope of the present invention is not limited by the examples, but is defined in the appended claims. All parts and percentages are based on weight unless otherwise indicated.

[0133] raw material

[0134] DP 450 is a polyether polyol with a Mw of 450 g / mol available from Kukdo Chemistry.

[0135] DP 2000M is a polyether polyol with a Mw of 2000 g / mol available from Kukdo Chemistry.

[0136] Castor oil is available from Ihsedu Agrochem.

[0137] XCP-355 is a polyester polyol derived from ethylene glycol, 1,4-butanediol, and adipic acid available from Xuchun Chemical (Suzhou) Co., Ltd.

[0138] PES 5622 is a polyester polyol available from Henkel derived from diethylene glycol, neopentyl glycol, 1,2-butanediol, 2-methyl-1,3-propanediol, sebacic acid, terephthalic acid, and succinic acid.

[0139] PES 9000 is a polyester polyol available from Henkel derived from monomers selected from ethylene glycol, neopentyl glycol, 1,4-butanediol, isophthalic acid and adipic acid, succinic acid.

[0140] Desmodur 44M is a polyisocyanate available from Covestro.

[0141] LIOFOL LA 6011 is a polyol mixture of polyester polyols and polyether polyols available from Henkel.

[0142] Sample preparation

[0143] The NCO-containing components (A) of the Examples and Comparative Examples were synthesized by the following steps using the raw materials listed in Tables 1 and 2:

[0144] (i) adding polyisocyanate into a reactor at 60° C. under the protection of nitrogen flow;

[0145] (ii) introducing a polyol into the reactor and controlling the water content in the reactor to be less than 300 ppm, and then gradually raising the temperature up to 80° C. and maintaining it for 2 to 3 hours; and

[0146] (iii) When the NCO content reaches the desired content, the produced NCO-containing component (A) is charged into a container at 60°C under the protection of nitrogen flow.

[0147] The NCO-containing component (A) prepared in Examples and Comparative Examples was mixed with the OH-containing component (B) listed in Table 1 or 2 to form an adhesive composition.

[0148] Test method:

[0149] Viscosity

[0150] The viscosity in the present invention is measured using a 27# spindle and a Brookfield viscometer at a temperature range of 50° C. A viscosity of less than 10,000 cps is acceptable.

[0151] Optical appearance

[0152] Laminated samples were prepared with these adhesive compositions in a laminating machine (SuperCombi 3000 available from Nordmeccanic). The adhesive compositions of the examples and comparative examples were heated to a temperature below 45°C and coated on a PET / aluminum foil (available from Guoao Foil Company, Shanghai, China) having a size of 1000 m*0.7 m. The coating weight was set to form a laminated sample having a thickness of 1.6 to 1.7 μm.

[0153] The laminated samples were cured at 45° C. for 48 hours. The optical appearance of the laminated samples was visually observed and determined based on the following ratings:

[0154] grade describe A No bubbles, shrinkage, spots or orange peel observed B Some small spots or bubbles can be visually observed without any orange peel or shrinkage C Obvious orange peel, shrinkage, many bubbles or quite a few small spots can be visually observed

[0155] A is preferred, and B may be acceptable.

[0156] Inventive Example 1 and Comparative Examples 1 to 3

[0157] In this set of examples, a solvent-free polyurethane adhesive composition of the present invention (Example 1) and three compositions having different NCO contents not within the scope of the claimed protection of the present invention (Comparative Examples 1 to Comparative Examples 3) were prepared based on the weight parts specified in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] Note: N / A means the composition could not adhere to the test layer due to high viscosity.

[0162] From Table 1 and the attached Figure 1 and 2 It can be seen that the compositions of Comparative Examples 1 to 3 whose NCO contents are not within the scope claimed in the present invention either have unsatisfactory optical appearance or have too high a viscosity to lack processability; while the composition of the present invention (Ex. 1) exhibits outstanding performance.

[0163] Inventive Examples 1 to 3 and Comparative Example 4

[0164] In this set of examples, the solvent-free polyurethane adhesive compositions of the present invention (Examples 1 to 3) and the composition having component (A) not within the claimed scope of the present invention (Comparative Example 4) were prepared based on the weight parts specified in Table 2.

[0165] Table 2

[0166]

[0167] As can be seen from Table 2, the composition having component (A) not within the scope of the claimed invention (Comparative Example 4) has an unsatisfactory optical appearance, while the compositions of the present invention (Examples 1 to 3) show good performance.

[0168] These and other modifications and variations of the present invention can be implemented by those of ordinary skill in the art without departing from the spirit and scope of the present invention. In addition, it should be understood that the various aspects of the various embodiments can be interchanged as a whole or in terms of reactants. Moreover, it will be understood by those of ordinary skill in the art that the above description is only as an example, rather than being intended to limit the present invention further described in the appended claims.

Claims

1. A solvent-free polyurethane adhesive composition comprising: (A) at least one isocyanate group-containing component comprising at least one isocyanate-terminated polyurethane prepolymer obtained by reacting a polyol mixture comprising: (a) at least one polyester polyol obtained by reacting a reactant mixture comprising: (i) at least one polycarboxylic acid selected from at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid, (ii) neopentyl glycol, and (iii) at least one polyol other than neopentyl glycol having a weight average molecular weight of 50 to 300 g / mol, and (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol, and (B) at least one hydroxyl-containing component; The NCO content of the isocyanate group-containing component (A) is greater than 10% by weight and less than 14% by weight.

2. The solvent-free polyurethane adhesive composition according to claim 1, wherein the polyester polyol (a) is modified with a vegetable oil selected from castor oil, soybean oil, palm oil, coconut oil and a combination thereof.

3. The solvent-free polyurethane adhesive composition according to claim 1 or 2, wherein the aliphatic dicarboxylic acid is a C2-C36 aliphatic dicarboxylic acid selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, dimer acid and their corresponding polycarboxylic acid anhydrides, and combinations thereof, preferably selected from adipic acid, sebacic acid, succinic acid, their corresponding polycarboxylic acid anhydrides, and combinations thereof.

4. The solvent-free polyurethane adhesive composition according to claim 1 or 2, wherein the aromatic dicarboxylic acid is a C8-20 aromatic dicarboxylic acid selected from isophthalic acid, terephthalic acid, bibenzoic acid and 2,6-naphthalene dicarboxylic acid, and their corresponding polycarboxylic acid anhydrides, and combinations thereof, preferably selected from isophthalic acid, terephthalic acid, their corresponding polycarboxylic acid anhydrides, and combinations thereof.

5. The solvent-free polyurethane adhesive composition according to claim 1 or 2, wherein the component (iii) at least one polyol having a weight average molecular weight of 50 to 300 g / mol other than neopentyl glycol is selected from ethylene glycol, diethylene glycol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, 1,2-propanediol, dipropylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, 2-butyl-2-ethylpropanediol, pentaerythritol, polytetramethylene ether glycol and combinations thereof, preferably selected from ethylene glycol, diethylene glycol, 1,2-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol and combinations thereof.

6. The solvent-free polyurethane adhesive composition according to claim 1 or 2, wherein the component (b) at least one polyether polyol having a weight average molecular weight of 200 to 4000 g / mol is selected from polytetramethylene ether glycol, poly(oxypropylene) glycol, polyethylene oxide, polybutylene oxide, and ethylene oxide-terminated forms of any of the foregoing substances, and combinations thereof, preferably selected from polytetramethylene ether glycol, poly(oxypropylene) glycol, ethylene oxide-terminated poly(oxypropylene) glycol, and combinations thereof. 7 . The solvent-free polyurethane adhesive composition according to claim 6 , wherein the weight average molecular weight (Mw) of the component (b) is 450 to 2,000 g / mol.

8. The solvent-free polyurethane adhesive composition according to any one of the preceding claims, wherein the polyisocyanate is selected from 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H12MDI), partially hydrogenated MDI (H6MDI), xylene diisocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), 4,4-diphenyldimethylmethane diisocyanate, dialkylene diphenylmethane diisocyanate, tetraalkylene diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, isomers of toluene diisocyanate (TDI), 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 1-methylisocyanatocyclohexane -3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), tetramethoxybutane-1,4-diisocyanate, naphthalene-1,5-diisocyanate (NDI), butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, 2,2,4-trimethylhexane-2,3,3-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, Ethylene diisocyanate, methylene triphenyl triisocyanate (MIT), diisocyanatoethyl phthalate, trimethylhexamethylene diisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane, dimer fatty acid diisocyanate, lysine ester diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 1,3-cyclohexane or 1,4-cyclohexane diisocyanate, and combinations thereof, preferably MDI.

9. The solvent-free polyurethane adhesive composition according to any one of the preceding claims, wherein the hydroxyl value of component (B) is in the range of 10 to 1500 mgKOH / g, preferably in the range of 56 to 560 mgKOH / g.

10. The solvent-free polyurethane adhesive composition according to any one of the preceding claims, wherein the component (B) is selected from polyester polyols, polyether polyols, polyester ether polyols, polycarbonate polyols, and combinations thereof.

11. The solvent-free polyurethane adhesive composition according to any one of the preceding claims, wherein the average hydroxyl functionality of component (B) is from 2 to 5, preferably from 2 to 4.

12. The solvent-free polyurethane adhesive composition according to any one of the preceding claims, wherein the mixing ratio of the component (A) to the component (B) is in the range of 5:100 to 19:1 parts by weight, preferably in the range of 50:100 to 200:100 parts by weight.

13. A laminate comprising a first layer, a second layer and an adhesive layer sandwiched therebetween, wherein the first and second layers are independently selected from films made of PET (polyethylene terephthalate), PP (polypropylene), OPP (oriented polypropylene), CPP (cast polypropylene), BOPP (biaxially oriented polypropylene), PE (polyethylene), aluminum foil, PA (polyamide), VMPET (vacuum metallized polyethylene terephthalate) and VMCPP (vacuum metallized cast polypropylene), preferably a film made of PET (polyethylene terephthalate) and aluminum foil, and the adhesive layer is formed by curing the adhesive composition according to any one of claims 1 to 12.

14. A food bag formed from the laminate of claim 13.

15. Use of the solvent-free polyurethane adhesive composition according to any one of claims 1 to 12 or the laminate according to claim 13 for producing food packaging.

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