Tackifiers for adhesive compositions

Abstract

The present invention relates to the use of a polyester comprising monomer repeat units from (A) a hydrogenated bisphenol, (B) a diol, (C) a dicarboxylic acid or anhydride thereof, where (C) comprises (C1) an aliphatic dicarboxylic acid or anhydride thereof, as a tackifier in an adhesive composition.

Description

[Technical field]

[0001] The present invention relates to the use of polyesters as tackifiers in radiation curable adhesive compositions. The present invention further relates to radiation curable adhesive compositions comprising such tackifiers and a radiation curable composition. The present invention further relates to articles comprising parts adhered together by the adhesive composition. [Background technology]

[0002] The use of tackifiers in adhesive compositions is known, and examples of known tackifiers include rosin, rosin esters, hydrogenated rosin esters, pure monomer resins, styrenic resins, and hydrogenated hydrocarbon resins.

[0003] US2005 / 0182150 discloses a radiation curable adhesive composition comprising at least one tackifier resin and at least one radiation curable composition. The tackifier resin may comprise repeating monomer units from at least one aromatic monomer and at least one acrylate monomer, more specifically repeating units from at least one monomer selected from styrene, acrylic acid, and 2-ethylhexyl acrylate. According to US2005 / 0182150, the problem of rosin being a skin sensitizer is solved by the described tackifier resin. However, according to the examples of US2005 / 0182150 (Tables 6 and 10.1), the tackifier resin provides peel adhesion and loop tack to the adhesive composition equivalent to rosin, and has higher UV absorption than rosin at the curing wavelength.

[0004] There remains a need in the art for tackifiers that impart good adhesive properties to adhesive compositions, preferably with low UV absorption and preferably are not skin sensitizers. It is also desirable for the tackifier to have good compatibility with the radiation curable composition in the adhesive composition. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a tackifier in which the above and / or other needs are met. [Means for solving the problem]

[0006] The present invention therefore provides the use of a polyester comprising monomer repeat units from (A) a hydrogenated bisphenol, (B) a diol and (C) a dicarboxylic acid or anhydride thereof, wherein (C) comprises (C1) an aliphatic dicarboxylic acid or anhydride thereof, as a tackifier in a radiation-curable adhesive composition.

[0007] The present invention further provides a radiation-curable adhesive composition comprising a tackifier and a radiation-curable composition, wherein the tackifier comprises or is a polyester comprising monomer repeat units from (A) a hydrogenated bisphenol, (B) a diol and (C) a dicarboxylic acid or anhydride thereof, and (C) comprises (C1) an aliphatic dicarboxylic acid or anhydride thereof.

[0008] The polyesters used in the present invention as tackifiers impart good adhesive properties to the adhesive composition, have low UV absorption, and are not skin sensitizers.

[0009] It is noted that JP2011225751A discloses a similar polyester. However, JP2011225751A relates to an ink containing 10-40% by weight of polyester, 30-75% by weight of UV-curable compound and 5-15% by weight of initiator, and does not relate to an adhesive composition. Suitable examples of (A) hydrogenated bisphenol, (B) diol and (C) dicarboxylic acid or anhydride thereof used in the present invention are described in JP2011225751A, which is incorporated herein by reference.

[0010] It will be understood by those skilled in the art that an adhesive composition is different from an ink. An ink requires a colorant and is not optically transparent. The adhesive composition according to the present invention is optically transparent. As used herein, the term "optically transparent" may refer to a material having a luminous transmittance of at least 80%, in particular at least 90%, in the wavelength range of 400-700 nm, and a haze of at most 5%, in particular at most 2%. The luminous transmittance and haze may be determined, for example, using ASTM-D 1003-95. It may also be defined by an opacity of at most 1% in the wavelength range of 400-700 nm, as determined by ASTM-D 1003-95. The adhesive composition according to the present invention may also be defined by it being substantially free of colorant, i.e., the adhesive composition comprises at most 0.1% by weight or 0% by weight of colorant.

[0011] The term "tackifier" as used herein means a composition useful for imparting tack to an adhesive composition or increasing the tack to a predetermined desired level or modifying the peel adhesion. ASTM D-1878-1T defines tack as "the property of a material that enables it to form a bond of measurable strength when in direct contact with another surface."

[0012] The term "radiation curable composition" as used herein means a composition that is curable upon exposure to actinic and / or ionizing radiation. The term "radiation" is used herein to include actinic radiation, such as ultraviolet radiation, and ionizing radiation produced by the emission of electrons or highly accelerated nuclear particles, such as neutrons and alpha particles. [Brief description of the drawings]

[0013] [Figure 1a] The x-axis is the wavelength (nm) from 230 to 300, and the y-axis is the absorbance from 0.00 to 2.00.

[0014] [Figure 1b]The x-axis is the wavelength (nm) from 230 to 300, and the y-axis is the absorbance from 0.00 to 2.00.

[0015] [Figure 1c] The x-axis is the wavelength (nm) from 230 to 300, and the y-axis is the absorbance from 0.00 to 2.00. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (A) Hydrogenated bisphenol

[0017] Suitable examples of hydrogenated bisphenols include bisphenol A (2,2-bis(4-hydroxyphenyl)propane), bisphenol F (bis(hydroxyphenyl)methane), bisphenol E (2,2-bis(4-hydroxyphenyl)ethane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol S (bis(4-hydroxyphenyl)sulfone), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, bis(4-hydroxyphenyl)phenanthane, bisphenol B (bis(4-hydroxyphenyl)butane), bisphenol S (bis(4-hydroxyphenyl)sulfone), bisphenol A (bis(4-hydroxyphenyl)propane), bisphenol F (bis(hydroxyphenyl)methane), bisphenol B (bis(hydroxyphenyl)butane), bisphenol S (bis(4-hydroxyphenyl)sulfone), bisphenol B ... Examples of such hydrides include hydrogenated bis(4-hydroxyphenyl)methane, bis(4-hydroxy-3,5-dimethylphenyl)methane, 1,1-bis(4-hydroxy-3,5-dimethylphenyl)ethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)butane, 2,2-bis(4-hydroxy-3-methylphenyl)butane, 1,1-bis(4-hydroxy-3-methylphenyl)-2-phenylethane, biphenol, bis(4-hydroxyphenyl)ether, and bis(4-hydroxyphenyl)ketone.

[0018] Further suitable examples of hydrogenated bisphenols include ethylene oxide and propylene oxide adducts of the examples of hydrogenated bisphenols described herein.

[0019] Preferably, the hydrogenated bisphenol is a hydrogenated bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

[0020] Preferably, the amount of (A) in the polyester is from 10 to 50% by weight, more preferably from 25 to 40% by weight, based on the weight of the polyester.

[0021] (B) Diol

[0022] Preferably, the diol is a diol having a branched alkyl group or an ether group.

[0023] Suitable examples of diols having branched alkyl groups include 2,2-dimethylpropane-1,3-diol (neopentyl glycol), 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-dimethylpentanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dimethylol octane, 2-ethyl-1,3-hexanediol, 2,5-diol-2,5-hexanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol and 2,4-diethyl-1,5-pentanediol.

[0024] Suitable examples of the diol having an ether group include polyethylene glycol (n=1 to 20), polypropylene glycol (n=1 to 20), polytetramethylene glycol (n=1 to 20), and polyether polyols such as polyester polyols.

[0025] Preferably, the diol is neopentyl glycol.

[0026] Preferably, the amount of (B) in the polyester is 10 to 50% by weight, more preferably 10 to 35% by weight, based on the weight of the polyester.

[0027] Preferably, the amount of (B) in the polyester is less than the amount of (A) in the polyester.

[0028] (C) Dicarboxylic acid or its anhydride

[0029] The dicarboxylic acid or anhydride thereof includes (C1) an aliphatic dicarboxylic acid or anhydride thereof.

[0030] Preferably, (C1) contains a cyclohexene or cyclohexane structure.

[0031] Suitable examples of (C1) include 1,2,3,6-tetrahydrophthalic acid, 3-methyl-1,2,3,6-tetrahydrophthalic acid, 4-methyl-1,2,3,6-tetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, and 4-methylhexahydrophthalic acid and their anhydrides.

[0032] Preferably, (C1) is 1,2,3,6-tetrahydrophthalic acid.

[0033] Preferably, (C) consists of (C1). Alternatively, (C1) may further comprise (C2) an aromatic dicarboxylic acid or an anhydride thereof, such as phthalic anhydride. It has been found that the presence of (C2) results in lower adhesive properties as well as higher UV absorption at the curing wavelength.

[0034] The amount of (C1) relative to (C) may be less than 50% by weight, for example less than 50% by weight and at least 10% by weight, at least 20% by weight, at least 30% by weight or at least 40% by weight. However, preferably, the amount of (C1) relative to (C) is at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight or 100% by weight. Preferably, the amount of (C2) relative to (C) is less than 50% by weight, less than 40% by weight, less than 30% by weight, less than 20% by weight, less than 10% by weight, less than 5% by weight or less than 1% by weight.

[0035] The amount of (C) in the polyester is preferably 20 to 60% by weight, more preferably 30 to 50% by weight, based on the weight of the polyester.

[0036] Preferably, the weight of (C) in the polyester is greater than the weight of (A) in the polyester. Preferably, the weight of (C) in the polyester is greater than the weight of (B) in the polyester. Preferably, the weight of (C) in the polyester is less than the sum of the weight of (A) in the polyester and the weight of (B) in the polyester.

[0037] The amount of (A) relative to the total amount of (A) and (C) is preferably 30 to 80% by weight, more preferably 35 to 75% by weight.

[0038] Preferably, the amount of (A) relative to the total of (A) and (B) is at most 70% by weight, more preferably 30 to 65% by weight, which provides particularly good compatibility with the other components in the adhesive composition.

[0039] Preferably, the amount of (A) relative to the total of (A) and (B) is at least 40% by weight, which provides high adhesive properties to the adhesive composition.

[0040] Other compounds for preparing polyesters

[0041] The polyesters used according to the invention may consist of monomer repeat units from (A), (B) and (C). Alternatively, the polyesters used according to the invention may further comprise monomer repeat units from compounds different from (A), (B) or (C). Preferably, the sum of the amounts of (A), (B) and (C) is 90-100 mol % of the polyester.

[0042] It will be understood that the amounts of (A), (B), and (C) in a polyester refer to the amount of each of (A), (B), and (C) used to prepare the polyester relative to the total amount of monomers used to prepare the polyester.

[0043] The polyesters used in accordance with the present invention may further comprise monomer repeat units from monohydric, dihydric, trihydric or higher alcohols, which may be linear or cyclic.

[0044] The polyesters used in accordance with the present invention may further include monomer repeat units from acid compounds such as monobasic and polybasic acids (aliphatic and aromatic polybasic acids).

[0045] polyester

[0046] Preferably, the polyester used according to the invention has a molar ratio of OH groups to COOH groups in the sum of (A), (B) and (C) of at least 1.3. This provides good compatibility with radiation curable compositions. Preferably, the molar ratio of OH groups to COOH groups is at most 1.9. In one embodiment, the polyester used according to the invention has a molar ratio of OH groups to COOH groups in the sum of (A), (B) and (C) of at most 0.7.

[0047] Preferably, the polyesters used according to the invention have an acid number of at least 60 mg KOH / g. More preferably, the polyesters used according to the invention have an acid number of at least 70 mg KOH / g, at least 80 mg KOH / g, at least 100 mg KOH / g or at least 120 mg KOH / g, determined according to ASTM D465-05(2010).

[0048] Such high acid numbers have been found to provide good compatibility with other components in the adhesive composition and good adhesive properties.

[0049] Preferably, the polyesters used according to the invention have an OH number, determined according to ASTM D4274-99, of at least 60 mg KOH / g. More preferably, the polyesters used according to the invention have an OH number, determined according to ASTM D4274-99, of at least 70 mg KOH / g, at least 80 mg KOH / g or at least 90 mg KOH / g. It has been found that such high OH numbers result in good compatibility with other components in the adhesive composition.

[0050] In a preferred embodiment, the polyester has an OH number of at least 70 mg KOH / g, determined according to ASTM D4274-99, and the amount of (A) relative to the sum of (A) and (C) is less than 70% by weight. Such polyesters have particularly good compatibility with other components in the adhesive composition.

[0051] In a preferred embodiment, the amount of (A) relative to the sum of (A) and (C) is at least 40% by weight, and the amount of (C1) relative to (C) is at least 50% by weight. Such polyesters have particularly good adhesive properties.

[0052] Adhesive Composition

[0053] The present invention further provides a radiation curable adhesive composition comprising or consisting of a tackifier comprising the polyesters described herein and a radiation curable composition.

[0054] Preferably, the amount of tackifier based on the total radiation curable adhesive composition is from 0.1 to 50% by weight, more preferably from 1 to 25% by weight.

[0055] The tackifier in the radiation curable adhesive composition may consist of a polyester or may further comprise one or more compounds known as tackifiers. Preferably, the amount of polyester relative to the total radiation curable adhesive composition is 0.1 to 50 wt%, more preferably 1 to 25 wt%.

[0056] Preferably, the amount of the radiation curable composition relative to the total radiation curable adhesive composition is 50 to 99.9% by weight, more preferably 75 to 99% by weight.

[0057] Radiation curable composition

[0058] Suitable examples of radiation curable compositions are described in US Patent Application Publication No. 2005 / 0182150, which is incorporated herein by reference.

[0059] Preferably, the radiation curable composition comprises an acrylic polymer.

[0060] Acrylic polymers include both homopolymers, copolymers, and terpolymers. The copolymers can be random, block, or graft.

[0061] The acrylic polymers are methyl acrylate, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, n-heptyl acrylate, n-heptyl methacrylate, 2-methylheptyl (meth)acrylate, octyl acrylate, octyl methacrylate, isooctyl (meth)acrylate. Acrylate, n-nonyl (meth)acrylate, iso-nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl acrylate, isodecyl methacrylate, dodecyl (meth)acrylate, isobornyl (meth)acrylate, lauryl methacrylate, lauryl acrylate, tridecyl acrylate, tridecyl methacrylate, stearyl acrylate, stearyl methacrylate, glycidyl methacrylate, alkyl crotonate, vinyl acetate, di-n-butyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate Acrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxypropyl acrylate, diacetone acrylamide, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, allyl methacrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, 2-ethoxyethyl acrylate, 2-ethoxy diethyl methacrylate, isodecyl methacrylate, isodecyl acrylate, 2-methoxy acrylate, 2-methoxy methacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, caprolactone acrylate, caprolactone methacrylate, benzyl acrylate, benzyl methacrylate, sodium 1-allyloxy-2-hydroxypropyl sulfonate,and mixtures thereof.

[0062] The acrylic copolymer may be produced by copolymerizing an acrylic monomer with a polar copolymerizable monomer. Examples of such polar copolymerizable monomers include cyanoalkyl acrylates, acrylamides, substituted acrylamides, N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, vinyl chloride, vinylidene chloride, and diallyl phthalate. The amount of the polar copolymerizable monomer may be, for example, 0-50% by weight, preferably 1-30% by weight, of the acrylic copolymer. The amount of the acrylic monomer may be, for example, 50-100% by weight, preferably 70-99% by weight, of the acrylic copolymer.

[0063] Preferably, the amount of acrylic polymer relative to the radiation curable composition is at least 75% by weight, more preferably from 80 to 99.9% by weight, more preferably from 90 to 99.5% by weight.

[0064] Other components in the radiation curable composition

[0065] The radiation curable adhesive composition may further comprise a photoinitiator and / or a crosslinker.

[0066] Examples of suitable photoinitiators include aldehydes, such as benzaldehyde, acetaldehyde, and their substituted derivatives; ketones, such as acetophenone, benzophenone, and their substituted derivatives; quinines, such as benzoquinone, anthraquinone, and their substituted derivatives; thioxanthones, such as 2-isopropylthioxanthone and 2-dodecylthioxanthone; and certain chromophore-substituted vinylhalomethyl-sym-triazines, such as 2-4-bis-(trichloromethyl)-6-(3',4'-dimethoxyphenyl)-sym-triazine.

[0067] Preferably, the amount of photoinitiator relative to the radiation curable composition is from 0.05 to 6.0% by weight, more preferably from 0.1 to 2.0% by weight, more preferably from 0.5 to 1.5% by weight.

[0068] Examples of suitable crosslinkers include substituted triazines such as 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s-triazine and the chromophore-substituted halomethyl-s-triazines disclosed in U.S. Patents 4,329,384 and 4,330,590, which are incorporated herein by reference. Other useful crosslinkers include multifunctional alkyl acrylate monomers such as, but not limited to, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, 1,2-ethylene glycol diacrylate, 1,6 hexanediol diacrylate, and 1,12-dodecanediol diacrylate.

[0069] Preferably, the amount of crosslinking agent relative to the radiation curable composition is 0.05 to 25% by weight, more preferably 0.1 to 10% by weight.

[0070] Preferably, the radiation curable composition comprising the acrylic polymer is UV light reactive, solvent-free and has a Tg of at most -32°C and a viscosity at 120°C of at most 24000 mPa·s.

[0071] Radiation-curable compositions comprising acrylic polymers and photoinitiators are commercially available. Examples of commercially available radiation-curable compositions include acResin® from BASF, such as acResin® A 204UV.

[0072] The radiation curable composition may further comprise at least one additive selected from the group consisting of toughening agents, flame retardants, blowing agents, plasticizers, oils, antioxidants and fillers. The radiation curable composition is substantially free of colorants.

[0073] Articles with glued parts

[0074] The invention further provides a method for adhering a first part and a second part, comprising contacting the first part and the second part with a radiation curable adhesive composition according to the invention and curing the radiation curable adhesive composition by radiation.

[0075] The invention further provides an article comprising a first part and a second part, the first part and the second part being adhered to one another by a process comprising contacting the first part and the second part with a radiation curable adhesive composition according to the invention and curing the radiation curable adhesive composition by radiation.

[0076] Preferably, the radiation is selected from ultraviolet light, electron beam, gamma rays and X-rays.

[0077] Preferably, the ultraviolet light has an effective ultraviolet wavelength in the range of about 100 nm to about 400 nm, preferably 220 nm to 280 nm, preferably 255 nm.

[0078] Preferably, the radiation is electron beam radiation in a dose ranging from about 1 megarad (Mrad) to about 30 Mrad.

[0079] Preferably, the first part and / or the second part are made of a material selected from the group consisting of polyethylene terephthalate, biaxially oriented polypropylene, woven fabrics, nonwoven fabrics, metals, metal foils, paper, glass, ceramics, and composite materials including laminates of one or more of these materials.

[0080] It is noted that, with respect to the subject matter defined by the independent claims alone or in combination with any possible combination of features described herein, particularly preferred are those combinations of features present in the claims.It will therefore be understood that all combinations of features relating to the composition according to the invention; all combinations of features relating to the method according to the invention, and all combinations of features relating to the composition according to the invention and features relating to the method according to the invention are described herein.

[0081] It is further noted that the term "comprising" does not exclude the presence of other elements. However, it should be understood that a description of a product / composition comprising certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous because it provides a simpler and more economical method for the preparation of the product / composition. Similarly, a description of a process comprising certain steps also discloses a process consisting of these steps. A process consisting of these steps may be advantageous because it provides a simpler and more economical method.

[0082] When values ​​are stated as lower and upper limits for a parameter, it is understood that the range formed by the combination of the lower limit value and the upper limit value is also disclosed.

[0083] The present invention will now be illustrated by the following examples, but is not limited thereto. EXAMPLES

[0084] Preparation of polyester

[0085] Examples 1-2

[0086] While nitrogen gas was blown into a four-neck flask equipped with a stirrer, a reflux condenser including a water separator, and a thermometer, bisphenol A (2,2-bis(4-hydroxyphenyl)propane) (HBA), neopentyl glycol (NPG), and 1,2,3,6-tetrahydrophthalic acid (THPA) were mixed therein and subjected to dehydration condensation at 230° C. for 6 hours. The weight ratios of HBA, NPG, and THPA are shown in Table 1. A polyester was obtained.

[0087] Comparative experiment 3

[0088] The process was identical to Example 1, except that no HBA was added and the weight ratios of the compounds used were different.

[0089] Comparative experiment 4

[0090] The process was identical to Example 1, except that phthalic acid was used instead of THPA and the weight ratios of the compounds used were different.

[0091] Various properties were measured on the resulting polyester.

[0092] The acid number was determined according to ASTM D465-05(2010).

[0093] Hydroxyl number was determined according to ASTM D4274-99.

[0094] compatibility

[0095] The resulting radiation curable adhesive composition comprising polyester and acrylic polymer (acResin 204UV) was mixed at 100° C. in a weight ratio of 20:80. The mixture was then cooled to room temperature and visually inspected for its transparency. If it is transparent, it is determined that the polyester is compatible with the radiation curable adhesive composition (indicated by O). If it is not transparent, it is determined that the polyester is not compatible with the radiation curable adhesive composition (indicated by X).

[0096] Adhesive properties

[0097] The resulting polyester and radiation curable adhesive composition containing an acrylic polymer (acResin 204UV) were mixed in a weight ratio of 20:80, and the mixture was dissolved in ethyl acetate (50% solution).

[0098] The solution was coated onto a PET substrate and dried in an oven at 110° C. The weight of the dried coating was 80 g / m 2 A 1 inch by 7 inch piece was prepared from the coated substrate and cured with UV-C (74 mJ).

[0099] The resistance to shear from standard surfaces (shear to SS) was determined according to FINAT FTM-8.

[0100] The loop tack was determined according to FINAT-9.

[0101] Peeling was determined according to FINAT-1.

[0102] [Table 1]

[0103] It can be seen that the polyesters according to the present invention (Examples 1 and 2) have good compatibility with acrylic polymers and good adhesive properties. The polyester of Comparative Example 3 has poor compatibility. The polyester of Comparative Example 4 has poor adhesive properties.

[0104] The same properties were measured for Foral 85 (a glycerol ester of highly hydrogenated wood rosin), whose adhesive properties were inferior to those of the polyester according to the invention.

[0105] The same properties were measured for acResin 204UV: the adhesive properties were significantly inferior to the polyester according to the invention.

[0106] UV absorption

[0107] UV absorption was measured for Polyester 1 and Polyester 2 (structures shown below) and Foral 85.

[0108] Polyester 1 [ka]

[0109] Polyester 2 [ka]

[0110] The UV absorption spectra for Polyester 1, Polyester 2 and Foral 85 are shown in Figures 1(a), 1(b) and 1(c), respectively. It can be seen that Polyester 1 according to the present invention has very low absorption at UV wavelengths.

Claims

1. 1. Use of a polyester comprising monomer repeat units from (A) a hydrogenated bisphenol, (B) a diol, and (C) a dicarboxylic acid or anhydride thereof, as a tackifier for an adhesive composition, wherein (C) comprises (C1) an aliphatic dicarboxylic acid or anhydride thereof.

2. 2. Use according to claim 1, wherein the polyester has an acid number of at least 60 mg KOH / g, as determined by ASTM D465-05(2010), and / or an OH number of at least 60 mg KOH / g, as determined by ASTM D4274-99, and preferably the amount of (A) relative to the total amount of (A) and (C) is 30-80 wt.-%, preferably 35-75 wt.-%.

3. the polyester has an acid number of at least 70 mg KOH / g as determined by ASTM D465-05(2010); or 3. The use according to claim 1 or 2, wherein the polyester has an OH number of at least 70 mg KOH / g as determined by ASTM D4274-99, and the amount of (A) relative to the sum of (A) and (B) is less than 70% by weight.

4. 3. Use according to claim 1 or 2, wherein the amount of (A) relative to the sum of (A) and (B) is at least 40% by weight and the amount of (C1) relative to (C) is at least 50% by weight.

5. the polyester has an acid number of at least 70 mg KOH / g; or 3. Use according to claim 1 or 2, wherein the amount of (A) relative to the sum of (A) and (B) is 40 to 70% by weight, and the amount of (C1) relative to (C) is at least 50% by weight.

6. the amount of (A) in the polyester is 10 to 50% by weight based on the weight of the polyester, the amount of (B) in the polyester is 10 to 50% by weight based on the weight of the polyester, and the amount of (C) in the polyester is 20 to 60% by weight, 3. Use according to claim 1 or 2, wherein preferably the amount of (C1) relative to (C) is at least 50% by weight, and preferably the total amount of (A), (B) and (C) relative to the polyester is at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight or 100% by weight.

7. (A) is Bisphenol A (2,2-bis(4-hydroxyphenyl)propane), bisphenol F (bis(hydroxyphenyl)methane), bisphenol E (2,2-bis(4-hydroxyphenyl)ethane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol S (bis(4-hydroxyphenyl)sulfone), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, bis(4-hydroxyphenyl)phenylmethane, biphenyl bis(4-hydroxy-3,5-dimethylphenyl)methane, 1,1-bis(4-hydroxy-3,5-dimethylphenyl)ethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)butane, 2,2-bis(4-hydroxy-3-methylphenyl)butane, 1,1-bis(4-hydroxy-3-methylphenyl)-2-phenylethane, biphenol, bis(4-hydroxyphenyl)ether and bis(4-hydroxyphenyl)ketone hydrides, The use according to claim 1 or 2, preferably selected from the group consisting of hydrides of bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

8. (B) is a diol having a branched alkyl group or an ether group, preferably 2,2-dimethylpropane-1,3-diol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-dimethylpentanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dimethylol octane, 2-ethyl-1,3-hexanediol, 2,5-diol-2,5-hexanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol and 2,4-diethyl-1,5-pentanediol and Polyethylene glycol (n=1 to 20), polypropylene glycol (n=1 to 20), polytetramethylene glycol (n=1 to 20), and polyester polyols; The use according to claim 1 or 2, preferably selected from the group consisting of 2,2-dimethylpropane-1,3-diol.

9. (C1) contains a cyclohexene or cyclohexane structure, preferably 1,2,3,6-tetrahydrophthalic acid, 3-methyl-1,2,3,6-tetrahydrophthalic acid, 4-methyl-1,2,3,6-tetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, and 4-methylhexahydrophthalic acid and their anhydrides, The use according to claim 1 or 2, preferably selected from the group consisting of 1,2,3,6-tetrahydrophthalic acid.

10. 1. A radiation-curable adhesive composition comprising a tackifier and a radiation-curable composition, wherein the tackifier comprises or is a polyester comprising monomer repeat units from (A) a hydrogenated bisphenol, (B) a diol having a branched alkyl group or an ether group, and (C) a dicarboxylic acid or an anhydride thereof, and (C) comprises (C1) an aliphatic dicarboxylic acid or an anhydride thereof.

11. 11. The radiation curable adhesive composition of claim 10, wherein the amount of said tackifier relative to the total radiation curable adhesive composition is 0.1 to 50 wt%, more preferably 1 to 25 wt%, and the amount of said radiation curable composition relative to the total radiation curable adhesive composition is 50 to 99.9 wt%, more preferably 75 to 99 wt%.

12. 12. The radiation curable adhesive composition according to claim 10 or 11, wherein the radiation curable composition comprises an acrylic polymer and preferably further a photoinitiator and / or a crosslinker, preferably the radiation curable adhesive composition comprises at most 0.1 wt.-% or 0 wt.-% of a colorant.

13. 12. The radiation curable adhesive composition according to claim 10 or 11, wherein the radiation curable adhesive composition has a luminous transmittance of at least 80% and a haze of at most 5% as determined by ASTM-D 1003-95 in the wavelength range of 400 to 700 nm.

14. 12. A method for adhering a first part and a second part, comprising contacting the radiation curable adhesive composition of claim 10 or 11 with the first part and the second part, and curing the radiation curable adhesive composition by radiation, preferably the radiation being selected from ultraviolet light, electron beam, gamma radiation and X-rays.

15. 12. An article comprising a first part and a second part, said first part and said second part being adhered to one another by a process comprising contacting the radiation curable adhesive composition of claim 10 or 11 with said first part and said second part, and curing said radiation curable adhesive composition by radiation, preferably said radiation being selected from ultraviolet light, electron beam, gamma radiation and X-rays.

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