WO2021209861A1

WO2021209861A1 - Acrylic pressure-sensitive adhesive composition, product thereof, and related preparation method therefor

Info

Publication number: WO2021209861A1
Application number: PCT/IB2021/052860
Authority: WO
Inventors: Xin Zhang; Yibo Zhou
Original assignee: 3M Innovative Properties Company
Priority date: 2020-04-16
Filing date: 2021-04-06
Publication date: 2021-10-21
Also published as: CN113528065B; CN113528065A

Abstract

The present invention provides an acrylic pressure-sensitive adhesive composition and a product thereof. The composition comprises 45 to 99.9 parts by weight of a polymer A, based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition, wherein the polymer A is a rosin resin grafted polyacrylate with a Tg of 0°C or below, a weight average molecular weight of 100,000 or above, and a polymer dispersity index of 7 or above; and the rosin resin has 1 to 15 parts by weight, based on 100 parts by weight of the polymer A. The present invention further relates to a method for synthesizing the acrylic pressure-sensitive adhesive composition. The acrylic pressure-sensitive adhesive composition and the product thereof according to the present invention are suitable for the bonding of low-surface-energy substrates, e.g., polyolefin and derivative materials such as polypropylene plates/films and polyethylene plates/films, and surfaces of functional coatings such as self-cleaning coatings, and have high bonding strength and bonding stability after high-temperature aging.

Description

ACRYLIC PRESSURE-SENSITIVE ADHESIVE COMPOSITION, PRODUCT THEREOF, AND RELATED PREPARATION METHOD THEREFOR

Technical Field

The present invention relates to an acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive product comprising the acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive glue comprising the acrylic pressure-sensitive adhesive composition, and a preparation method for a rosin resin grafted polyacrylate with a weight average molecular weight of 100,000 or above and a polymer dispersity index of 7 or above for synthesizing the acrylic pressure-sensitive adhesive composition.

Background

In the field of adhesives, bonding solutions for low-surface-energy substrates comprise: structural glues, foam adhesive tapes, and pressure -sensitive adhesives (PSAs). Structural glues have a high bonding force but may damage the surface (may usually cause surface swelling or corrosion), which is not suitable for bonding substrates with high appearance requirements and low thickness. Foam adhesive tapes are thick, porous, and expensive. In order to achieve a good wetting ability of the existing pressure-sensitive adhesives (PSAs) on low-surface-energy substrate surfaces, the modulus and cohesion of the adhesives need to be sacrificed, resulting in low bonding strength, holding power, and/or bonding stability, and poor resistance to high temperatures.

In view of the above defects, in one technical solution, a small-molecular rosin resin is mixed into a high-modulus pressure-sensitive adhesive, to enhance the bonding force between the pressure-sensitive adhesive and a low-surface-energy substrate, and the chain motion of a polymer is enhanced through chain entanglement of the plasticized polymer, thereby improving the ability of the pressure-sensitive adhesive to wet the surface. However, the small-molecular rosin resin will migrate to the interface with time and/or under the action of a high temperature, reducing the cohesion force and bonding stability of the pressure-sensitive adhesive. Such a pressure-sensitive adhesive has a poor holding power, bonding stability, and resistance to high temperatures.

Therefore, attempts were made to fix a small-molecular rosin resin onto a polymer matrix to reduce migration. For example, acrylate monomers are grafted on a rosin resin, followed by further copolymerization with a glue system of acrylate. However, the rosin resin itself carries a large number of active hydrogen atoms, and the acrylate monomers with rosin resin side chains hanged also have great steric hindrance, seriously impacting chain growth of the polymer. At present, it is only possible to obtain rosin grafted polyacrylates with a very small molecular weight, which are not suitable for use as oligomers in adhesives. For example, with regard to the method of modifying a rosin resin with an acrylate monomer, Chinese Invention Patent Applications CN 106479367 A (Paragraph [0004] in Summary and Paragraph [0007] in Examples) and CN 107254023 A (Paragraph [0017] in Summary and Paragraph [0065] in Examples) mention that an acrylate monomer is used to modify a rosin resin, in which the rosin resin is mixed with the acrylate monomer to perform modification at a high temperature (e.g., a temperature of 120°C or above), to obtain a rosin resin grafted acrylate monomer.

Although the impact of the rosin resin can be partially shielded by adding a substance with a core-shell structure during emulsion polymerization, the shielding effect is limited. The rosin grafted acrylate polymer obtained by emulsion polymerization is mainly used as a dispersant for hydrogel systems. For example, with regard to the preparation of a rosin resin modified acrylate hydrogel, Chinese Invention Patent Application CN 103059212 A (Paragraph [0005] in Summary) mentions a hydrogenated rosin resin modified acrylate emulsion; and CN 107236496 A (Paragraph [0004] in Summary) mentions an optically transparent structural adhesive of a rosin resin modified polyurethane-acrylate, where acrylic acid, acrylate monomers, and acrylamide are polymerized and nucleated in an emulsion. However, in processes that have been industrialized currently, a reactive rosin resin will directly participate in the polymerization of acrylates. The biggest difficulty is that the chain transfer effect of the rosin resin affects the molecular weight of polymers, rendering it impossible to form a pressure-sensitive adhesive glue with sufficiently strong cohesion. In emulsion polymerization systems, this chain transfer effect will be alleviated to a certain extent by a core-shell structure (reaction from inside to outside), but the molecular weight (weight average molecular weight less than 100,000 Daltons) and the adhesion (70°C, lxl inch, and holding time less than 1000 min at a 1-kg weight) of the product obtained are insufficient to serve as an adhesive.

Therefore, it is still desired in the art to provide a pressure-sensitive adhesive glue for bonding low-surface-energy substrates that has good bonding strength, holding power, and/or bonding stability, and good high-temperature aging resistance.

Summary

In view of the above bonding problem between low-surface-energy substrates and other materials (including low-surface-energy materials), the present invention provides a novel acrylic pressure-sensitive adhesive composition, and a pressure-sensitive adhesive product obtained with the novel acrylic pressure-sensitive adhesive composition, which have good bonding strength, bonding stability, and high-temperature aging resistance for low-surface-energy substrates, such as polypropylene plates or films.

Therefore, according to one aspect of the present invention, an acrylic pressure-sensitive adhesive composition is provided, comprising 45 to 99.9 parts by weight of a polymer A, based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition, wherein the polymer A is a rosin resin grafted polyacrylate with a Tg of 0°C or below, a weight average molecular weight of 100,000 Daltons or above, and a polymer dispersity index of 7 or above; and the rosin resin has 1 to 15 parts by weight, based on 100 parts by weight of the polymer A.

According to another aspect of the present invention, a pressure-sensitive adhesive product is provided. The pressure-sensitive adhesive product comprises a substrate; and a coating of the foregoing acrylic pressure-sensitive adhesive composition coated on at least one surface of the substrate.

According to still another aspect the present invention, an acrylic pressure-sensitive adhesive is provided. The acrylic pressure-sensitive adhesive comprises the foregoing acrylic pressure-sensitive adhesive composition and an organic solvent.

According to a further aspect the present invention, a preparation method for a rosin resin grafted polyacrylate with a weight average molecular weight of 100,000 Daltons or above and a polymer dispersity index of 7 or above is provided. The preparation method comprises:

1) prepolymerizing 50 to 89 parts by weight of a C4-C18 alkyl (meth)acrylate monomer (a), 5 to 12 parts by weight of one or a plurality of styrene or a-methylstyrene or a (meth)acrylic cyclic ethylenically-unsaturated monomer (b), and 0.85 to 9.5 parts by weight of a polymerizable acidic monomer (c) in an organic solvent, to obtain a prepolymer AA with an intrinsic viscosity ranging from 0.6 to 1.0 dl/g; and

2) adding 1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d), 1 to 25 parts by weight of a C4-C18 alkyl (meth)acrylate monomer (a), and 0.15 to 0.5 parts by weight of a polymerizable acidic monomer (c) into the obtained prepolymer AA to carry out polymerization, to obtain a rosin resin grafted polyacrylate A with a weight average molecular weight Mw of 100,000 Daltons or above and a polymer dispersity index of 7 or above.

In the present invention, the rosin resin grafted acrylate polymer A with a Tg of 0°C or below, a weight average molecular weight of 100,000 Daltons or above, and a polymer dispersity index of 7 or above is used as a raw material to prepare the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition has high bonding strength and high bonding stability for low-surface-energy substrates (e.g., polypropylene plates, polyethylene films, self-cleaning coatings, low-surface-energy coatings, etc.), and exhibits excellent overall performance, including: 180° peeling force, high-temperature holding, high-temperature and high- humidity aging resistance, etc.

Further, the formula of the pressure -sensitive adhesive composition of the present invention can also adapt to different surfaces and different bonding requirements by compounding the rosin resin grafted acrylate polymer A with other raw materials/aids. Because the rosin resin is grafted on the high-molecular-weight polyacrylate polymer, an obvious and stable plasticizing effect is achieved; therefore, the pressure -sensitive adhesive composition provided in the present invention has desirable holding performance and aging resistance under ultra-high temperatures (greater than 100°C).

Detailed Description

In view of the bonding problem between low-surface-energy substrates and other materials, a rosin resin grafted acrylate polymer A with a sufficiently high molecular weight and polymer dispersion index and a relatively low glass transition temperature is polymerized in a solvent environment by the present invention. The rosin resin grafted acrylate polymer A has a high intrinsic viscosity and a great molecular weight. It is blended with a polymer B having a relatively high glass transition temperature or other raw materials such as a crosslinker or a tackifier, to produce an acrylic pressure-sensitive adhesive composition.

As used herein, the term “(meth)acrylic acid” refers to acrylic acid, methacrylic acid, or both. Similarly, the term “(meth)acrylate” refers to an acrylate, a methacrylate, or both. The term “(meth)acrylate polymer” refers to a polymer in which polymerizable monomers are mainly acrylic acid/acrylate and/or methacrylic acid/methacrylate. Accordingly, a C4-C18 alkyl (meth)acrylate monomer means a C4-C18 alkyl acrylate monomer and/or a C4-C18 alkyl methacrylate monomer, and a (meth)acrylic cyclic ethylenically-unsaturated monomer means an aliphatic cyclic or aromatic cyclic acrylate monomer and/or an aliphatic cyclic or aromatic cyclic methacrylate monomer.

As used herein, a C4-C 18 alkyl refers to an alkyl having 4 to 18 carbon atoms, including isomeric forms thereof, e.g., «-butyl, /-butyl, /-decyl, «-hexadecyl, and 2-octadecyl.

Polymer A

The acrylic pressure -sensitive adhesive composition provided in the present invention comprises a polymer A which is a rosin resin grafted polyacrylate with a glass transition temperature of 0°C or below, a weight average molecular weight Mw of 100,000 Daltons or above, and a polymer dispersity index of 7 or above. The polymer A comprises 1 to 15 parts by weight of the rosin resin, based on 100 parts by weight of the polymer A.

According to certain specific embodiments of the present invention, preferably the polymer A has a polymer dispersity index (PDI) of 3 or above, or 7 above; and the polymer A has a polymer dispersity index of 11 or below, or 10 or below. If the PDI is excessively small, e.g., less than 3, the balance of the bonding and cohesion strength of pressure-sensitive adhesive components is excessively poor, rendering it difficult to balance the holding power and the surface wettability; and if the PDI is excessively high, e.g., greater than 11, the small molecular weight distribution of the pressure-sensitive adhesive components is excessively great, and the cohesion is insufficient, rendering it difficult to achieve a holding effect.

According to certain specific embodiments of the present invention, preferably the polymer A has a glass transition temperature of 0°C or below, or -30°C or below, or -40°C or below, or -50°C or below. If the glass transition temperature is greater than 0°C, it is very difficult for the polymer to develop chain motion at room temperature, rendering it impossible to effectively wet a bonding surface.

According to certain specific embodiments of the present invention, the polymer A has a weight average molecular weight M_w of 100,000 Daltons or above, preferably 300,000 Daltons or above, or 400,000 Daltons or above; and preferably, the polymer A has a weight average molecular weight M_w of 1,000,000 Daltons or below, or 700,000 Daltons or below. If the value of Mw is excessively low, e.g., less than 100,000 Daltons, the chain entanglement of the adhesive is insufficient to produce sufficient cohesion, consequently failing to provide an effective peeling force and holding power.

According to certain specific embodiments of the present invention, the content of the polymer A in the acrylic pressure-sensitive adhesive composition of the present invention is not less than 45 parts by weight, or not less than 80 parts by weight, or not less than 90 parts by weight, and the content of the polymer A is not more than 99.9 parts by weight, based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition. When the lower limit of the content of the polymer A is in line with the above range, the pressure-sensitive adhesive system can have good wettability; and when the upper limit of the content of the polymer A is in line with the above range, the pressure-sensitive adhesive system has good high-temperature performance and holding power. Additionally, the acrylic pressure-sensitive adhesive composition comprising the polymer A in the above content has high bonding strength and high bonding stability, and can exhibit excellent overall performance, including 180° peel force, high-temperature adhesion, high- temperature and high-humidity aging resistance, etc.

According to certain specific embodiments of the present invention, and based on 100 parts by weight of the polymer A, the polymer A comprises 1 part by weight or more of a rosin resin. In order to better control the molecular weight of the polymer A, the content of the rosin resin in the polymer A is preferably 5 parts by weight or above, but 15 parts by weight or below. This is because when the content of the rosin resin is excessively high, it may be difficult to control chain growth and grafting, which may lead to an excessively low molecular weight, resulting in a degraded holding power and stability of the pressure -sensitive adhesive composition. According to certain specific embodiments of the present invention, preferably the polymer A is prepared by polymerization of polymerizable monomers comprising 75 to 90 parts by weight of a C4-C18 alkyl (meth)acrylate monomer (a), 5 to 12 parts by weight of one or a plurality of styrene or a-methylstyrene or a (meth)acrylic cyclic ethylenically-unsaturated monomer (b), 1 to 10 parts by weight of a polymerizable acidic monomer (c), and 1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d), based on 100 parts by weight of the polymerizable monomers.

According to some examples of the present invention, preferably the C4-C18 alkyl (meth)acrylate monomer (a) comprises one or a plurality of items selected from the group consisting of «-butyl (meth)acrylate, /-butyl (meth)acrylate, «-amyl (meth)acrylate, /-amyl (meth)acrylate, 2-methylbutyl (meth)acrylate, «-hexyl (meth)acrylate, 4-methyl-2-amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methylhexyl (meth)acrylate, «-octyl (meth)acrylate, /-octyl (meth)acrylate, 2-octyl (meth)acrylate, z-nonyl (meth)acrylate, z- amyl (meth)acrylate, «- decyl (meth)acrylate, z-decyl (meth)acrylate, 2-propylheptyl (meth)acrylate, z-tridecyl (meth)acrylate, z-stearyl (meth)acrylate, octadecyl (meth)acrylate, 2-octadecyl (meth)acrylate, lauryl (meth)acrylate, and heptadecyl (meth)acrylate.

The glass transition temperature of the (meth)acrylate cyclic ethylenically-unsaturated monomer (b) is not particularly limited, and is preferably 60 to 190°C when measured as a homopolymer. The monomer (b) is an ethylenically-unsaturated monomer having a ring structure in the molecule. As the ring in the cyclic ethylenically-unsaturated monomer, an aromatic ring or a non-aromatic ring may be used, but it is suitable to select a non-aromatic ring. Examples of aromatic rings comprise aromatic hydrocarbon rings (e.g., a benzene ring and a fused ring in naphthalene, etc.) and various heteroaromatic rings. In addition, examples of non-aromatic rings comprise non-aromatic aliphatic rings (e.g., cycloalkane rings, such as a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, and a cyclooctane ring; and cycloalkene rings, such as a cyclohexene ring) and non-aromatic crosslinked rings (e.g., crosslinked hydrocarbon rings, including bicyclic hydrocarbon rings of pinane, pinene, camphane, norcamphane, norcamphene, etc.; tricyclic hydrocarbon rings in adamantane; and tetracyclic hydrocarbon rings). Specifically, examples comprise a (meth)acrylate containing a non-aromatic ring, e.g., a cycloalkyl (meth)acrylate (e.g., cyclohexyl (meth)acrylate) and z-bomyl (meth)acrylate; and a (meth)acrylate containing an aromatic ring, e.g., an aryl (meth)acrylate (e.g., phenyl acrylate), an aryloxyalkyl (meth)acrylate (e.g., phenoxyethyl (meth)acrylate), and an arylalkyl (meth)acrylate (e.g. benzyl (meth)acrylate).

According to certain specific examples of the present invention, preferably the (meth)acrylic cyclic ethylenically-unsaturated monomer (b) comprises one or a plurality of items selected from the group consisting of a cycloalkyl (meth)acrylate (e.g., cyclohexyl (meth)acrylate), 7-bomyl (meth)acrylate, an aryl (meth)acrylate (e.g., phenyl acrylate), an aryloxyalkyl (meth)acrylate, and an arylalkyl (meth)acrylate, or a mixture thereof with styrene and/or a- methylstyrene.

According to certain specific examples of the present invention, the polymerizable acidic monomer (c) refers to a polymerizable monomer containing an acid functional group (typically carboxy), and preferably comprises one or a plurality of items selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, oleic acid, b-carboxylethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and vinyl phosphonic acid.

According to certain specific examples of the present invention, the rosin resin modified free-radical polymerizable monomer refers to a monomer in which a rosin resin is linked to a free- radical polymerizable monomer by grafting. Preferably, a rosin resin modified acrylic monomer in which a rosin resin is linked to an acrylic monomer by grafting is typical.

In the present invention, according to certain specific examples, the polymer A can be synthesized using a two-step method:

In the first step, by using an effective temperature and solid content (the effective temperature and solid content refer to a temperature and solid content used to control the molecular weight of a prepolymer in the first polymerization reaction step), without adding the rosin resin modified free-radical polymerizable monomer (d), all of styrene or a-methylstyrene or (methyl)acrylic cyclic ethylenically-unsaturated monomer (b) and most of the C4-C 18 alkyl (meth)acrylate monomer (a) and most of the polymerizable acidic monomer (c) are polymerized to increase the molecular weight to a sufficient length, to obtain a prepolymer AA, wherein the intrinsic viscosity of the prepolymer AA ranges from 0.6 to 1.0 dl/g.

In the second step, all of the rosin resin modified free-radical polymerizable monomer (d) and the remaining portion of the monomers (a) and (c) together with a desired initiator are added into the prepolymer AA obtained in the previous step, and a solvent is used to adjust the temperature and solid content, so that the monomer (d) is linked to the long-chain polymer, or forms a new short chain with the remaining monomers, thus forming a wide molecular weight distribution. In subsequent coating, the addition of a curing agent can further fix the rosin resin onto the long molecular chain, to form a rosin grafted acrylate polymer with a molecular weight of 100,000 Daltons or above.

More specifically, a preparation method for a rosin resin grafted polyacrylate with a weight average molecular weight of 100,000 Daltons or above and a polymer dispersity index of 7 or above comprises: 1) prepolymerizing 50 to 89 parts by weight of the C4-C18 alkyl (meth)acrylate monomer (a), 5 to 12 parts by weight of the (meth)acrylic cyclic ethylenically-unsaturated monomer (b), and 0.85 to 9.5 parts by weight of the polymerizable acidic monomer (c) in an organic solvent, to obtain the prepolymer AA with an intrinsic viscosity ranging from 0.6 to 1.0 dl/g; and

2) adding 1 to 10 parts by weight of the rosin resin modified free-radical polymerizable monomer (d), 1 to 25 parts by weight of the C4-C18 alkyl (meth)acrylate monomer (a), and 0.15 to 0.5 parts by weight of the polymerizable acidic monomer (c) into the obtained prepolymer AA to carry out polymerization, to obtain a rosin resin grafted polyacrylate A with a weight average molecular weight Mw of 100,000 or above and a polymer dispersity index (PDI) of 7 or above.

According to certain specific examples of the present invention, preferably the polymer A solution prepared has a solid content of 40 to 50 wt%. The solid content can be adjusted by a suitable solvent.

The polymer A prepared in the present invention is a rosin resin grafted polyacrylate with a weight average molecular weight of 100,000 Daltons or above and a polymer dispersity index (PDI) of 7 or above. The polymer A is different from a simple mixture of a rosin resin and an acrylate monomer. Through NMR detection, it can be seen in the pattern that the absorption peaks of the polymer A prepared by the present invention change obviously, and the absorption peak corresponding to acrylic double bonds disappears obviously, indicating that the rosin resin is successfully grafted onto the polyacrylate molecule, thereby preparing a high-molecular-weight rosin resin grafted polyacrylate.

Polvmer B

The acrylic pressure -sensitive adhesive composition provided in the present invention further comprises a polymer B which is a polyacrylate with a glass transition temperature of 60°C or above and more preferably 80°C or above.

According to certain specific embodiments of the present invention, the content of the polymer B in the acrylic pressure -sensitive adhesive composition of the present invention is not less than 5 parts by weight, and preferably not less than 10 parts by weight, and the content of the polymer B is not more than 50 parts by weight, and preferably not more than 30 parts by weight, based on 100 parts by weight of the acrylic pressure -sensitive adhesive composition. When the content of the polymer B is within the above range, the pressure-sensitive adhesive composition prepared can have a good high-temperature holding effect and peeling force.

According to certain specific examples of the present invention, preferably the polymer B is prepared by polymerization of polymerizable monomers comprising 90 to 99 parts by weight of one or a plurality of styrene or a-methylstyrene or a (meth)acrylic cyclic ethylenically-unsaturated monomer (b), 1 to 10 parts by weight of a polymerizable acidic monomer (c), and optionally 0.1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d), based on 100 parts by weight of the polymerizable monomers.

According to certain specific examples of the present invention, preferably the (meth)acrylate cyclic ethylenically-unsaturated monomer (b) comprises one or a plurality of items selected from the group consisting of a cycloalkyl (meth)acrylate (e.g., cyclohexyl (meth)acrylate), 7-bomyl (meth)acrylate, an aryl (meth)acrylate (e.g., phenyl acrylate), an aryloxyalkyl (meth)acrylate, and an arylalkyl (meth)acrylate, or a mixture thereof with styrene and/or a- methylstyrene.

According to certain specific examples of the present invention, the polymerizable acidic monomer (c) refers to a polymerizable monomer containing an acid functional group (typically carboxy), and preferably comprises one or a plurality of items selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, oleic acid, b-carboxylethyl methacrylate, styrene sulfonic acid , 2-acrylamido-2-methylpropane sulfonic acid, and vinyl phosphonic acid.

According to certain specific examples of the present invention, the rosin resin modified free-radical polymerizable monomer (d) refers to a monomer in which a rosin resin is linked to a free-radical polymerizable monomer by grafting. Preferably, a rosin resin modified acrylic monomer in which a rosin resin is linked to an acrylic monomer by grafting is typical.

According to certain specific examples of the present invention, preferably the polymerizable monomers of the polymer B comprise 0.1 to 10 parts by weight of the rosin resin modified free-radical polymerizable monomer (d), and the polymer B has a weight average molecular weight of 7,000 to 25,000 Daltons.

According to certain specific examples of the present invention, the polymerizable monomers of the polymer B comprise no rosin resin modified free-radical polymerizable monomer (d), and the polymer B has a weight average molecular weight of 7,000 to 50,000 Daltons.

In the present invention, according to certain specific examples, similarly to the above polymer A, the polymer B may also be synthesized using a two-step method, particularly when the polymerizable monomers of the polymer B comprise 0.1 to 10 parts by weight of the rosin resin modified free-radical polymerizable monomer (d):

1) prepolymerizing 75 to 95 parts by weight of the monomer (b) and 0.75 to 9.0 parts by weight of the monomer (c) in an organic solvent to synthesize a prepolymer BB; and

2) adding 4 to 15 parts by weight of the monomer (b), 0.25 to 1.0 parts by weight of the polymerizable acidic monomer (c), and optionally 0.1 to 10 parts by weight of the monomer (d) into the obtained prepolymer BB to carry out a polymerization reaction, so as to prepare the polymer B.

In the present invention, there is no special restriction on the polymerization method for obtaining the polymer A or B through monomer polymerization, and the polymer can be prepared by any conventional polymerization or copolymerization method, e.g., the desired polymer can be prepared by photoinitiated free-radical polymerization. The photopolymerization method has advantages in that: (1) it is not necessary to heat a monomer solution; and (2) when an activation light source is turned off, light initiation is completely stopped. A monomer conversion rate in the system (a ratio of the weight of polymerized monomers to the weight of all monomers used to prepare the polymer) can be achieved by controlling the amount of a photoinitiator, and the polymerization can be terminated by quenching the growing free radicals through removing the light source and introducing air (oxygen) to the solution. The photoinitiator used may comprise: benzoin methyl ether, benzoin isopropyl ether, 2,2-dimethoxyacetophenone, 2,2-dimethoxy-2- phenyl-1 -acetophenone, V-67 (available from DuPont Company), etc. A solution polymerization method may also be adopted, in which the desired monomer and the photoinitiator may be placed together with a suitable inert organic solvent into a four-neck reaction vessel equipped with a mixer, a thermometer, a condenser, a feed hopper, and a temperature controller, to carry out polymerization.

In the present invention, preferably, after the polymer A and the polymer B are obtained, the polymer B is added into the polymer A and then blended. A small amount of a solvent, e.g., a mixed solvent of isopropanol/xylene (in which xylene is less than 5 mass%), can be used as required, to improve the solubility. After several minutes of oscillation in a THINKY mixer, the polymers are mixed overnight on a three-roll machine. Preferably, before a curing crosslinker is added into the pressure-sensitive adhesive composition obtained, the system is uniform and transparent.

Optional additives

According to some examples of the present invention, the acrylic pressure-sensitive adhesive composition may further comprise an additive selected from the group consisting of a tackifier, a crosslinker, an ultraviolet absorber, an antioxidant, a light stabilizer, an anti-aging agent, a thickening agent, a plasticizer, a softening agent, a filler, a colorant (e.g., a pigment and a dye), a surfactant, and an antistatic agent.

In the present invention, although not necessary, other additives may be added to the obtained adhesive composition, with the proviso that such additives will not have adverse impact on desired characteristics. For example, a compatible tackifier or crosslinker may be added to help the optimization of the final adhesion force and the peeling-off property of the PSA. The use of such viscosity modulating agents is common in the art, e.g., as mentioned in Handbook of Pressure-Sensitive Adhesive Technology (1982) edited by Donatas Satas. Tackifiers that can be used in this invention comprises, but not limited to, low-molecular-weight hydrocarbon polymers, hydrogenated rosin resin and rosin resin. Examples of tackifiers that can be used comprise, but are not limited to, Escorez 1401 available from Exxon Mobil, GB-125 available from Arakawa Chemical Industries, GER-85/PER-90/PER-110F available from Wuzhou Sun Shine Forestry & Chemicals, etc. Crosslinkers that can be used comprise aromatic bis-amide compound (e.g. RD1054 available from 3M Company), polyfunctional aziridine liquid crosslinker (e.g. CX-100, available from DSM Company), etc.

In the present invention, preferably, the composition obtained is cured and crosslinked.

The curing and crosslinking can be performed as follows: after the polymers A and B are mixed uniformly, a 0.1-0.2% crosslinker (e.g., RD1054, CX-100, or RD1054+CX-100) is added into the transparent A+B system. The mixture is mixed for e.g., about 1 h on a three-roll machine and THINKY.

In the present invention, preferably, a UV stabilizer known in the art may be further added. The pressure-sensitive adhesive composition provided by the present invention may further comprise a pigment. The pressure-sensitive adhesive composition provided by the present invention may further comprise expanded polymer particles or expanded polymer microspheres, so as to improve the forward drop-impact resistance of the prepared pressure-sensitive adhesive layer. These expanded polymer particles or expanded polymer microspheres generally have a particle diameter of 10 to 100 microns. For example, metallized expanded polymer particles may be selected to give the pressure-sensitive adhesive layer the desired color, appearance, and additional foam-like properties. The pressure -sensitive adhesive composition provided by the present invention may further comprise a plasticizer, a dye, an antioxidant, a coupling agent, a dispersing agent, an anti-settling agent, etc., provided that performance of the pressure -sensitive adhesive and the pressure-sensitive adhesive layer further prepared by using the pressure-sensitive adhesive composition is not affected. In order to improve the die-cutting performance of the pressure- sensitive adhesive layer, some short synthetic fibers may also be added to the pressure-sensitive adhesive composition provided that the drop-impact resistance of the pressure -sensitive adhesive layer is not affected.

In the present invention, although there is no special restriction, preferably, the pressure- sensitive adhesive composition of the present invention is non-aqueous, e.g., it may be a 100% solid (pressure-sensitive adhesive) or a mixture with a non-aqueous solvent (pressure-sensitive adhesive glue). In addition, the adhesive composition generally contains no surfactant.

The present invention further provides a pressure-sensitive adhesive product. In the present invention, the pressure-sensitive adhesive composition may be coated onto a suitable substrate or carrier, and then the coated pressure-sensitive adhesive composition is exposed to ultraviolet radiation to form a pressure -sensitive adhesive layer, to produce the pressure-sensitive adhesive product, e.g., a pressure -sensitive adhesive sheet or a pressure-sensitive adhesive tape. The substrate or carrier may be rigid, flexible, transparent, or opaque, and may be prepared from any suitable material (such as polymer materials, glass or ceramic materials, and metals). In some preferred embodiments, the substrate or carrier may be a polymer material, such as a flexible polymer film of a flexible backing. Suitable polymer materials may comprise: polyolefins (e.g., polyethylene, or polypropylene (including isotactic polypropylene)), polystyrene, polyesters (e.g., poly(ethylene terephthalate), poly(butylene terephthalate), polylactide, or poly (caprolactam)), nylon, polyvinyl alcohol, poly(vinylidene fluoride), or cellulose (e.g., cellulose acetate or ethyl cellulose). The flexible substrate or carrier may have a specific micro-structured surface such as those mentioned in US Patents US 5141790 (Calhoun et al.), US 5296277 (Wilson et al.), or US 5362516 (Wilson et al.). These micro-structured surfaces are typically available through micro replication techniques. The substrate or carrier may also be prepared from a fabric (such as, a fabric formed of synthetic fibers or natural fibers). The fabric may be woven or non-woven. The suitable fibers may comprise cotton, nylon, rayon, glass, or ceramic. In addition, other suitable substrate or carriers may further comprise metal sheets, metal foils, metalized polymer films, ceramic sheets, or foams (e.g., acrylic foams, polyethylene foams, polyurethane foams, or neoprene foams).

In the present invention, the pressure-sensitive adhesive composition may be coated onto the substrate or carrier with any suitable method (e.g., roll coating, flow coating, dip coating, spin coating, spray coating, knife coating, or die coating). These different coating methods allow coating of the pressure-sensitive adhesive composition of various suitable thicknesses onto the substrate or carrier. The coating thickness may vary, and a typical thickness of the pressure- sensitive adhesive layer may range from 2 to 500 microns, and may also range from 25 to 250 microns. In the present invention, preferably, a standard sample for testing is a 50 pm adhesive film plus 50 pm PET, with a 10 g/inch release film protecting the surface of the adhesive film.

In the present invention, preferably, the pressure -sensitive adhesive product may further comprise a release paper or release film which covers the surface of the acrylic pressure-sensitive adhesive composition and is removed before use. Such products may, for example, be obtained as follows: extruding the pressure-sensitive adhesive composition to coat on the surface of a substrate (preferably pre-cleaned), so as to form a flat pressure-sensitive adhesive composition layer, and then attaching the release paper onto the surface of the pressure-sensitive adhesive composition layer. The present invention further provides a pressure-sensitive adhesive glue, comprising the acrylic pressure-sensitive adhesive composition according to any of the above examples, and an organic solvent.

In the present invention, there is no particular restriction on the organic solvent used in the pressure-sensitive adhesive glue, provided that the pressure-sensitive adhesive desired can be prepared. Preferably, the organic solvent used in the present invention may be one or a plurality of items selected from the group consisting of ethyl acetate, butyl acetate, methyl formate, ethyl formate, methyl acetate, propyl acetate, isopropanol, acetone, butanone, toluene, xylene, petroleum ether, «-hexane, and cyclohexane.

Since the polymer A in the acrylic pressure -sensitive adhesive composition provided in the present invention is grafted with a rosin resin and has a high molecular weight, the pressure- sensitive adhesive product or the pressure-sensitive adhesive glue obtained in the present invention can be desirably used for the bonding of low-surface-energy substrates, which comprise but are not limited to one or a plurality of items selected from the group consisting of polypropylene materials, polyethylene materials, polyurethane materials, and polycarbonate materials. More particularly, the pressure-sensitive adhesive product or the pressure-sensitive adhesive glue of the present invention may be used for, for example, film application on the surface of a self-cleaning steel plate of an automobile body, film application on the surface of a Thermo-Plastic Vulcanizate primer, film application on the surface of automotive interior plastic parts, bonding of a polypropylene plate, bonding of a polyethylene film, and/or bonding of a polypropylene outer package.

In the present invention, unless otherwise specified, when a range is referred to, both end values of the range and its subranges shall be understood to be all included in the range.

Examples

Examples and comparative examples provided hereinafter facilitate the understanding of the present invention and should not be construed as limiting the scope of the present invention. Unless stated otherwise, all parts, percentages, ratios, concentrations, and the like in the examples and in the rest part of the description are given by weight, and all agents used in the examples are obtained from or available from general chemical suppliers or can be synthesized through conventional methods.

The raw materials used in the examples and comparative examples of the present invention are shown in Table 1. Table 1

Testing method and standard:

Glass transition temperature (Tg) determination Glass transition temperatures (Tg) are determined with a differential scanning calorimeter

(DSC) (Q100, commercially available from TA Instruments Co. Ltd., Delaware, US). Each sample is lowered to -80°C, then maintained at the condition of -80°C for 2 min, and then heated to 40°C (or to 100°C) at a rate of 10°C/min. Tg corresponds to a peak temperature from a glassy state to a liquid state.

Intrinsic viscosity (IV) measurement

Viscosity is mainly used to characterize the molecular weight of a macromolecule (blend), and the test process thereof is as follows: a 0.5 g/dl dilute solution sample of a pressure-sensitive composition is prepared in ethyl acetate. 25.00 mL of the dilute solution is pipetted into a 70-mL aluminum dish and dried in a forced air oven at 105°C for 30 min, and the weight of the dried polymer is recorded as w. 9 g of ethyl acetate is pipetted into a Cannon-Fenske viscometer and the flow time (to) is measured by a Schott-Gerate AVS 400 electronic timer, and at the same time the flow time (t_s) of the dilute solution sample of the same weight is also measured. The intrinsic viscosity IV is calculated based on the measured values of w, to, and t_s with the following formula:

RV = to / t_s

I Vo = (LnRV) / 4w

IV = 0.2 [(RV - 1) / 4w - IVo)](l - 0.5 / 4w) + IVo

Ln represents a natural logarithm.

Polymer molecular weight (including number average molecular weight Mn and weight average molecular weight Mw) test:

Sample preparation and test method: A sample is dissolved at a concentration of 20 mg/4 ml in a tetrahydrofuran standard solution. After gently shaken to accelerate the dissolution, the sample is kept overnight to ensure the dissolution.

Test conditions - equipment: Waters 2695-MALS; chromatographic column: Jordi-DVB 30 cm x 7.8 mm; column temperature: 40°C; solvent: a tetrahydrofuran standard solution; flow rate: 1.0 ml/min; injected sample volume: 40 mΐ; test: Refractive Index; standard sample: polystyrene.

The polymer dispersity index (PDI) is defined as PDI = Mw / Mn.

180° peeling force test

The 180° peel force of a pressure -sensitive adhesive prepared is measured on the surface of polypropylene (PP), a self-cleaning coating lacquer plate (carbamate), and a standard stainless steel plate respectively, in accordance with the standard in ASTM D3330/D3330M.

Measurement of static shear hold time at 70°C

The 70°C static shear hold time is used to characterize the cohesion of a macromolecule. A longer time indicates better cohesion. Its testing procedure is as specified in ASTM International Standard D3654. Specifically, a test sample is prepared as follows: a 1-kg rubber roller is rolled back and forth once on a 25.4 mm * 25.4 mm pressure-sensitive adhesive tape, so as to adhere the adhesive film to the surface of an alumina plate cleaned with IPA. Then a 1-kg load is loaded under the test sample, and then hanged vertically in a drying oven at 70°C. The time recorded during the test is a hold time during which the test sample does not fall off from the surface of the alumina plate under the action of the load. If the hold time is greater than 10,000 min, the sample is marked as good; if the hold time is 1,000 min to 10,000 min, the sample is marked as qualified; and if the hold time is less than 1,000 min, the sample is marked as unqualified. Alternatively, comparison may be performed among particular times, to determine the relative level.

70°C holding power test on 304 steel plate/PP/low-surface-energy lacquer plate

A 1 inch * 1 inch standard sample is attached onto the surface of a PP/lacquer plate/steel plate, and a 1-kg weight is hanged vertically thereto at 70°C. If the hold time is greater than 10,000 min, the sample is marked as good; if the hold time is 1,000 min to 10,000 min, the sample is marked as qualified; and if the hold time is less than 1,000 min, the sample is marked as unqualified.

85°C/85% RH aging test

The adhesive tape attached to the lacquer plate/steel plate together with the substrate is placed into an oven at 85°C/85% relative humidity, and then the aged sample is used for one or a plurality of the above tests, and the relative level of aging resistance is determined by comparing the difference of performance before and after the aging.

80°C long-term aging test

The adhesive tape protected with the release paper is placed into an oven at 80°C and aged for 4 weeks, and then the aged sample is used for one or a plurality of the above tests, and the relative level of aging resistance is determined by comparing the difference of performance before and after the aging.

120°C high-temperature aging test

The adhesive tape protected with the release paper is placed into an oven at 120°C and aged for 5 days, and then the aged sample is used for one or a plurality of the above tests, and the relative level of aging resistance is determined by comparing the difference of performance before and after the aging.

In all performance tests (Table 7 to Table 11), each of the result values is an average value of 3 measurements.

Preparation of polymer A

Synthesis example 1 :

1) 1098.2 g (75.2 parts by weight) of an /-octyl acrylate monomer (a), 169 g (11.6 parts by weight) of an 7-bomyl acrylate monomer (b), and 34.9 g (2.4 parts by weight) of an acrylic monomer (c) were added into an organic solvent (848.6 g of ethyl acetate, and 565.8 g of butyl acetate), and reacted for 8 h in the presence of an initiator benzoin methyl ether, at 58°C under the protection of nitrogen gas, to obtain a prepolymer AA with an intrinsic viscosity ranging from 0.6 to 1.0 dl/g; and

2) in a nitrogen atmosphere, the temperature of a reaction kettle was increased to 80°C, then 76.8 g (5.3 parts by weight) of a TSR-0065 monomer (d), 153.6 g (10.5 parts by weight) of an /-octyl acrylate monomer (a), and 3.5 g (0.2 parts by weight) of an acrylic monomer (c) were added into the reaction kettle to mix with the prepolymer AA obtained from step 1), with the solid content adjusted to 45 wt% using a solvent (149.8 g of ethyl acetate and 99.8 g of butyl acetate).

Oxygen gas was removed using nitrogen gas, and reaction was performed for 24 h in the presence of a polymerization initiator benzoin methyl ether, to obtain a final product A, recorded as A1.

The preparation method of samples A2 and A3 of a rosin resin grafted polyacrylate polymer A is the same as that of Al, and the particular formulas and process parameters are shown in Table 2:

Synthesis example 2:

In 1569 g of an organic solvent ethyl acetate, 1245.6 g (86.6 parts by weight) of an /-octyl acrylate monomer (a), 158.4 g (11.0 parts by weight) of an 7-bomyl acrylate monomer (b), and 34.6 g (2.4 parts by weight) of an acrylic monomer (c) were reacted for 24 h in the presence of an initiator benzoin methyl ether, at 58°C under the protection of nitrogen gas, to obtain a polyacrylate polymer, recorded as CA1.

5 The synthesis steps of CA2 were the same as those of CA1, except that 76.8 g (5.3 parts by weight) of a TSR-0065 monomer (d) was added to polymerization monomers.

Table 2

10 is 24 hrs.

Comparative sample CA1 contained no rosin resin.

Comparative sample CA2 had completely the same formula as sample Al. All the monomers were polymerized in a single step together, to directly obtain comparative sample CA2, instead of firstly preparing a prepolymer with an intrinsic viscosity ranging from 0.6 to 1.0 dl/g and then polymerizing the prepolymer with the remaining monomers by using a two-step method.

The above samples A 1 to A3 and comparative samples CA1 and CA2 of the polymer A were measured for molecular weights, and the results are shown in the following Table 3 :

Table 3

It can be seen from Table 3 that, the rosin resin grafted polyacrylate polymers A 1 to A3 prepared in the present invention had a number average molecular weight (Mn) ranging from 50,000 to 80,000 Daltons, and a weight average molecular weight (Mw) of greater than 100,000 Daltons, ranging from 400,000 to 700,000 Daltons, and a PDI (Mw/Mn) of greater than 7, ranging from 7 to 11.

Preparation of polymer B

As shown in the following Table 4, in the presence of a polymerization initiator, and under the protection of nitrogen gas, 90 wt% of a monomer (b) and 80 wt% of a monomer (c) were polymerized in a solvent in a reaction kettle at 65°C for 8 h, to obtain a prepolymer; and a rosin resin modified monomer (d) obtained by grafting to an acrylate monomer was dissolved in the remaining monomers (b) and (c), and the final solid content and molecular weight were adjusted using a solvent. In a nitrogen atmosphere, the temperature was increased to 85°C, then the remaining monomers (b) and (c) and the monomer (d) (i.e., TSR-0065 or TSR-6000 commercially available from Tone Resin Chemical Co., Ltd.) were added into the obtained prepolymer. After the addition, oxygen gas was removed using nitrogen gas, and a polymerization reaction was performed for 8 h in the presence of a polymerization initiator, thus obtaining a polymer B.

Samples B 1 and B2 of the polymer B were prepared according to the above reaction process, where B2 contained no rosin resin.

Formulas and process parameters are shown in Table 4: Table 4

Note: the solid content (wt%) of all the samples is 25.

The above samples B1 to B2 of the polymer B were measured for molecular weights, and the results are shown in the following Table

5:

5

Table 5

Preparation of pressure-sensitive adhesive compositions

(Examples El to E5 and Ell to E14, and Comparative examples Cl to C3 and Cll to C16)

10 After the polymer B or a crosslinker/tackifier was added into the polymer A, the mixture was mixed for 12 h on a three-roll machine, so as to obtain a desired pressure-sensitive adhesive composition. A small amount of a mixed solvent, e.g., isopropanol/xylene (in which xylene is less than 5 mass%), can be used as required, to improve the solubility. The formulas of particular pressure-sensitive adhesive compositions are shown in Tables 6-1 and 6-2.

Table 6-1. Table of ingredient combinations of pressure-sensitive adhesive composition (polymer

A + polymer B) samples

Table 6-2. Table of ingredient combinations of pressure-sensitive adhesive composition (polymer A + crosslinker/tackifier) samples

Performance test of pressure-sensitive adhesive compositions

The obtained pressure-sensitive adhesive compositions were tested for 180° peel forces and 180° peel forces after aging, and subjected to basic performance comparison. The results are shown in Table 7 to Table 9 below.

Table 7-1 shows the 180° peeling forces of Examples El, E2, and E5, and Comparative examples Cl and C3 on a lacquer finish and a white standard lacquer plate.

Table 7-1

In Table 7-1, a 180° peeling force of greater than 0.7 on the LSE lacquer finish and a 180° peeling force of greater than 0.8 on the standard white lacquer finish are regarded as qualified. Considering that a pressure -sensitive adhesive should also meet high-temperature adhesion performance requirements, a preferred failure mode order is: separation from substrate > vibration > separation from backing base > cohesive failure.

In Comparative example Cl and Comparative example C3, the polymer CA1 containing no rosin or the polymer CA2 prepared by the traditional one-step method was used, while in Examples El, E2, and E5, the rosin grafted high-molecular-weight polymer A3 or A1 was used. As shown in Table 7-1, the use of the rosin grafted high-molecular-weight polymer in the pressure- sensitive adhesive composition can improve the 180° peeling force.

Table 7-2

In Table 7-2, a 180° peeling force of greater than 0.50 on the LSE lacquer finish and a 180° peeling force of greater than 0.7 on the standard white lacquer finish are regarded as qualified. Considering that a pressure -sensitive adhesive should also meet high-temperature adhesion performance requirements, a preferred failure mode order is: separation from substrate > vibration > separation from backing base > cohesive failure.

The polymer CA1 containing no rosin was used in Comparative examples Cll and C12. The polymer CA1 containing no rosin and the rosin modified monomer TSR-0065 were used in Comparative example C15. The polymer CA2 prepared through the one-step method was used in Comparative example Cl 6, and the failure mode thereof was cohesive failure.

The polymers A3, A2, and A1 were used respectively in Examples Ell, E13, and E14, and the pressure-sensitive adhesive compositions prepared with a crosslinker mixed had better 180° peeling forces on the LSE lacquer finish and the standard white lacquer finish.

Table 8-1

Table 8-2

The aging in Tables 8-1 and 8-2 was performed by attaching a pressure-sensitive adhesive on a substrate. The 180° peeling forces of the pressure-sensitive adhesive composition on the lacquer finish and the standard plate after 600 hours aging at 85°C/85%RH were tested. As high temperatures promote wetting, the peeling forces increased further. After the 600 hours aging at 85°C/85%RH, a 180° peeling force of greater than 1.00 on the LSE finish and a 180° peeling force of greater than 1.20 on the standard white lacquer finish are regarded as qualified.

The rosin grafted high-molecular-weight polymer A3 was used in all of Examples El, E2, and Ell, and the polymer CA1 containing no rosin was used in Comparative examples Cl 1 and C12. It can be seen that, the examples using the high-molecular-weight polymer containing the grafted rosin exhibited an obvious bonding advantage, and had good high-temperature and high- humidity aging resistance, both before and after the aging. Ell lacks a high-Tg polymer to improve the cohesion, and the failure mode changed to cohesive failure.

Table 9-1

Table 9-2

*PO represents interface detachment; CF represents cohesive failure; S represents shock; + represent over; and CP represents separation from substrate.

Tables 9-1 and 9-2 show comparison of the basic performance (180° peeling force, and 70°C static adhesion) of Examples El, E4, and E12, and Comparative examples Cl, C2, C3 and Cll, C12, C16.

The rosin grafted high-molecular-weight polymer A3 and the polymer B2 were used in Examples El and E4. The rosin grafted high-molecular-weight polymer A3 was used in Example El 2. It can be seen that, when a pressure-sensitive adhesive composition contains the combination of the polymer A and the polymer B, it can have both a good peeling force and a good holding power at the same time. The reason is that when the polymer B is added, effective crosslinking and curing are formed, and the holding power at high temperature can also be improved. It can be seen from Comparative example C3 that, because the polymer A synthesized with the one-step method was used, though the formula contained a rosin resin, the pressure-sensitive adhesive suffered from severe cohesive failure in the high-temperature static shear test and had poor holding properties due to migration of the rosin resin. Table 10-1

Note: CP represents separation from substrate, and CF represents cohesive failure. Table 10-2

Note: CP represents separation from substrate, and CF represents cohesive failure.

Table 10-1 and 10-2 show the results of the 180° peeling force test performed again after the pressure-sensitive adhesives prepared were coated onto a 50 pm PET film and directly kept in an oven at 80°C for 4 weeks. Compared with the peeling force before aging, a drop percentage lower than 20% was regarded as qualified.

The rosin grafted macromolecular polymer A1 and the polymer CA1 synthesized through the one-step method were used respectively in Example E5 and Comparative example C3. It can be seen that the drop in 180° peeling force after aging of E5 was less.

The rosin grafted macromolecular polymers A3, A2, and A1 were used respectively in Examples E12, E13, and E14, and though the polymer B was not added, the drops in 180° peeling force after aging of the corresponding pressure-sensitive adhesive compositions were all less than 20%.

Table 11-1: Changes in 180° peeling force after 5-dav aging at 120°C

Table 11-2: Changes in 180° peeling force after 5-dav aging at 120°C

Table 11-1 and 11-2 show that the prepared pressure-sensitive adhesives were coated onto a 50 pm PET fdm, directly placed in an oven at 120°C and aged for 5 days, and the 180° peeling forces before and after the aging were tested.

The rosin grafted macromolecular polymer A 1 and the polymer CA1 synthesized through the one-step method were used respectively in Example E5 and Comparative example C3. It can be seen that the drop in 180° peeling force after aging of E5 was less.

The rosin grafted macromolecular polymers A3, A2, and A1 were used respectively in Examples E12, E13, and E14, and though the polymer B was not added, the drops in 180° peeling force after aging at 120°C of the corresponding pressure-sensitive adhesive compositions were all less than 20%.

Though not bound by specific theories, the inventor of the present invention holds that the possible reason why the present invention can have the above beneficial effects is that, in an ordinary blending system, a rosin resin is blended and dispersed in polymer molecules, whether in an initial mixture, a polymerized and crosslinked mixture, or an aged mixture, and only plays the role of swelling and increasing a bonding force. In a long-term aging process, the low-molecular- weight rosin resin migrates to the surface and accumulates under the action of surface energy and polymer chain entanglement, degrading the adhesion performance and stability. In the present invention, a rosin resin is grafted on a long chain of acrylate, to prepare a high-molecular-weight polymer. In an initial mixture, a polymerized and crosslinked mixture, and an aged mixture, the rosin resin is fixed on the long chain of acrylate by chemical bonds, and is difficult to form free migration; even after an aging process, the rosin resin can remain stable, thereby enhancing the aging stability.

Though the above specific embodiments comprise a great many concrete details for the purpose of illustration through examples, it is to be understood by those of ordinary skill in the art that, many variations, modifications, replacements, and changes to these details shall all fall within the scope of the present invention as claimed in the claims. Therefore, the disclosure as described in the specific embodiments does not pose any limitation to the present invention as claimed in the claims. The proper scope of the present invention should be defined by the claims and proper legal equivalents thereof. All references referred to are incorporated herein by reference in their entireties.

Claims

What is claimed is:

1. An acrylic pressure -sensitive adhesive composition, comprising 45 to 99.9 parts by weight of a polymer A, based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition, wherein the polymer A is a rosin resin grafted polyacrylate with a Tg of 0°C or below, a weight average molecular weight of 100,000 or above, and a polymer dispersity index of 7 or above; and the rosin resin has 1 to 15 parts by weight, based on 100 parts by weight of the polymer A.

2. The acrylic pressure-sensitive adhesive composition according to claim 1, further comprising 5 to 50 parts by weight of a polymer B that is a polyacrylate with a glass transition temperature of 60°C or above, based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition.

3. The acrylic pressure-sensitive adhesive composition according to any of claim 1 or 2, wherein the polymer A has a glass transition temperature of -40°C or below.

4. The acrylic pressure-sensitive adhesive composition according to any of claim 1 or 2, wherein the polymer A has a weight average molecular weight Mw of 400,000 to 700,000.

5. The acrylic pressure-sensitive adhesive composition according to any of claim 1 or 2, wherein the acrylic pressure-sensitive adhesive composition comprises 80 to 90 parts by weight of the polymer A.

6. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the polymer A is prepared by polymerization of polymerizable monomers comprising 75 to 90 parts by weight of a C4-C18 alkyl (meth)acrylate monomer (a), 5 to 12 parts by weight of one or a plurality of styrene or a-methylstyrene or a (meth)acrylic cyclic ethylenically-unsaturated monomer (b), 1 to 10 parts by weight of a polymerizable acidic monomer (c), and 1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d).

7. The acrylic pressure-sensitive adhesive composition according to claim 2, wherein the polymer B is prepared by polymerization of polymerizable monomers comprising 90 to 99 parts by weight of a (meth)acrylic cyclic ethylenically-unsaturated monomer (b), 1 to 10 parts by weight of a polymerizable acidic monomer (c), and optionally 0.1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d).

8. The acrylic pressure-sensitive adhesive composition according to claim 6, wherein the C4-C18 alkyl (meth)acrylate monomer (a) comprises one or a plurality of items selected from the group consisting of «-butyl (meth)acrylate, /-butyl (meth)acrylate, «-amyl (meth)acrylate, z- amyl (meth)acrylate, 2-methylbutyl (meth)acrylate, «-hexyl (meth)acrylate, 4-methyl-2-amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methylhexyl (meth)acrylate, «-octyl (meth)acrylate, /-octyl (meth)acrylate, 2-octyl (meth)acrylate, z-nonyl (meth)acrylate, /-amyl (meth)acrylate, «- decyl (meth)acrylate, z-decyl (meth)acrylate, 2-propylheptyl (meth)acrylate, z-tridecyl (meth)acrylate, z-stearyl (meth)acrylate, octadecyl (meth)acrylate, 2-octadecyl (meth)acrylate, lauryl (meth)acrylate, and heptadecyl (meth)acrylate.

9. The acrylic pressure-sensitive adhesive composition according to claim 6 or 7, wherein the (meth)acrylic cyclic ethylenically-unsaturated monomer (b) comprises one or a plurality of items selected from the group consisting of a cycloalkyl (meth)acrylate (e.g., cyclohexyl (meth)acrylate), z-bomyl (meth)acrylate, an aryl (meth)acrylate (e.g., phenyl acrylate), an aryloxyalkyl (meth)acrylate, and an arylalkyl (meth)acrylate.

10. The acrylic pressure-sensitive adhesive composition according to claim 6 or 7, wherein the polymerizable acidic monomer (c) comprises one or a plurality of items selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, oleic acid, b-carboxyethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2- methylpropane sulfonic acid, and vinyl phosphonic acid.

11. The acrylic pressure-sensitive adhesive composition according to claim 7, wherein the polymerizable monomers of the polymer B comprise 0.1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d), and the polymer B has a weight average molecular weight Mw of 7,000 to 25,000.

12. The acrylic pressure-sensitive adhesive composition according to claim 7, wherein the polymerizable monomers of the polymer B comprise no rosin resin modified free-radical polymerizable monomer (d), and the polymer B has a weight average molecular weight of 7,000 to 50,000.

13. A pressure-sensitive adhesive product, comprising: a substrate; and a coating of the acrylic pressure-sensitive adhesive composition according to any of claims 1 to 12 coated on at least one surface of the substrate.

14. The pressure-sensitive adhesive product according to claim 13, wherein the pressure-sensitive adhesive product further comprises a release paper or release fdm covering the coating surface of the acrylic pressure-sensitive adhesive composition.

15. An acrylic pressure -sensitive adhesive glue, comprising the acrylic pressure- sensitive adhesive composition according to any of claims 1 to 12, and an organic solvent.

16. The acrylic pressure-sensitive adhesive glue according to claim 15, wherein the acrylic pressure-sensitive adhesive glue has a solid content of 20 wt% to 70 wt%.

17. The acrylic pressure-sensitive adhesive glue according to claim 15 or 16, wherein the organic solvent is one or a plurality of items selected from the group consisting of ethyl acetate, butyl acetate, methyl formate, ethyl formate, methyl acetate, propyl acetate, isopropanol, acetone, butanone, toluene, xylene, petroleum ether, «-hexane, and cyclohexane.

18. A preparation method for a rosin resin grafted polyacrylate with a weight average molecular weight of 100,000 or above and a polymer dispersity index of 7 or above, the preparation method comprising:

2) adding 1 to 10 parts by weight of a rosin resin modified free-radical polymerizable monomer (d), 1 to 25 parts by weight of a C4-C18 alkyl (meth)acrylate monomer (a), and 0.15 to 0.5 parts by weight of a polymerizable acidic monomer (c) into the obtained prepolymer AA to carry out polymerization, to obtain a rosin resin grafted polyacrylate A with a weight average molecular weight Mw of 100,000 or above and a polymer dispersity index of 7 or above.