WO2012094885A1

WO2012094885A1 - Solventless silicone pressure sensitive adhesive and preparation method thereof

Info

Publication number: WO2012094885A1
Application number: PCT/CN2011/077843
Authority: WO
Inventors: 李彦民
Original assignee: 深圳市森日有机硅材料有限公司
Priority date: 2011-01-13
Filing date: 2011-08-01
Publication date: 2012-07-19
Also published as: CN102174309B; CN102174309A

Abstract

Disclosed is a solventless silicone pressure sensitive adhesive, comprising: 100 parts by mass of a polydimethylsiloxane having an alkenyl group as an end group; 1 to 300 parts by mass of a polydimethylsiloxane having a hydroxyl group as an end group; 1 to 50 parts by mass of MQ resin; 1 to 30 parts by mass of polyisobutylene, 20 to 200 parts by mass of a diluent; 0.1 to 5 parts by mass of a crosslinking agent and a platinum catalyst capable of solidifying the silicone pressure sensitive adhesive. Also disclosed is a preparation method for the silicone pressure sensitive adhesive. The silicone pressure sensitive adhesive disclosed has the characteristics of good initial tackiness, long effectiveness, suitable peel-off strength and good drug permeability, is non-toxic and environmentally-friendly, is capable of repeated use, can be made into pressure sensitive adhesive tapes, pressure sensitive adhesive strips for medical use, as well as other functional materials where such pressure sensitive properties are required.

Description

Solvent-free silicone pressure sensitive adhesive and preparation method thereof

Technical field

The invention relates to a silicone pressure sensitive adhesive and a preparation method thereof, in particular to a solventless silicone pressure sensitive adhesive which has good initial tack, long-lasting effect, suitable peel strength and drug release property.

Background technique

Pressure Sensitive Adhesive (PSA) is an adhesive that achieves good adhesion in a short period of time by applying a finger pressure. It wets surfaces as quickly as fluids and prevents peeling like solids. It is widely used in the production of adhesive tapes, pressure sensitive labels, hygiene products and other products of the same type. Typical characteristics of pressure sensitive adhesives are their shear strength, peel strength, tack and adhesive transferability (i.e., the amount of adhesive remaining after tape removal). Silicone pressure sensitive adhesives not only have the good bond strength and initial tack necessary for pressure sensitive adhesives, but also many unique properties such as good adhesion to high energy and low energy surface materials to untreated hardly viscous materials. Such as PTFE, etc. have good bonding properties; with outstanding high and low temperature resistance, can be used for a long time between -73 ° C ~ 296 ° C; good shear strength, acceptable initial tack of the probe And room temperature folding shear; has good chemical inertness, long service life, and has outstanding moisture resistance and electrical properties; has a certain liquid permeability and biological inertness, can be used to treat the adhesion of drugs to human skin.

The silicone PSA is usually composed of a silicone rubber, an MQ type silicone resin (containing M unit R ₃ SiO _1/2 and Q chain SiO _4/2 ), a crosslinking agent, a catalyst, an organic solvent, and the like.

The silicone pressure sensitive adhesive used earlier is a low solids solvent type pressure sensitive adhesive. The conventional solvents are toluene, xylene, dichlorotoluene, petroleum ether, and mixtures thereof. There have been many patent reports on solvent-based silicone pressure-sensitive adhesives. For example, U.S. Patent No. 5,939,477 describes the dissolution of silicone resins and polydimethylsiloxane with solvents such as trichlorofluoromethane, hexane, benzene, xylene, and the like. A mixture of oxyalkylene (hydroxyl-terminated), after concentration, is concentrated by adding polyisobutylene having a terminal hydroxyl group, and the solvent is evaporated to prepare a pressure-sensitive adhesive, which is applied to a substrate for vulcanization. Another U.S. Patent No. 5,612,400 describes the use of linear and cyclic organosiloxane monomers in place of volatile organic solvents to synthesize silicone pressure sensitive adhesives. In this method, the advantage is that organosiloxanes can be used. As a non-polluting, recyclable carrier, the disadvantage is that the cost is too high, which is not conducive to popularization. Although the solvent-based silicone pressure-sensitive adhesive has excellent performance, it requires a large amount of solvent, consumes a large amount of raw materials and energy, and at the same time, causes environmental pollution to a certain extent.

Among the components of the silicone pressure-sensitive adhesive, a polymer-quality silicone rubber is responsible for the viscosity of the product. To increase the solids content, it is necessary to use a low viscosity silicone rubber, that is, a low molecular weight silicone rubber, but this will reduce the performance of the pressure sensitive adhesive and even lose pressure sensitivity. Nowadays, low-viscosity vinyl polydimethylsiloxane or (and) low-viscosity hydroxypolysiloxane is generally used instead of the original high-viscosity polysiloxane, and the MQ resin is used to form a cured silicone pressure-sensitive adhesive. It not only improves the solid content, but also has good bonding properties. U.S. Patent No. 7,997,433 B2 describes vinyl terminated polydimethylsiloxane (degree of polymerization 300-2000) and silicone resin (containing R ¹ ₃ SiO _1/2 monomer and SiO _4/2 monomer). a phenolic inhibitor (or phenol-modified polydimethylsiloxane) and an aromatic amino-based inhibitor (or an aromatic amino-modified polydiene) in a mixture or partial condensation product having a molar ratio of 0.5 to 1.5) Methyl siloxane), which is cured by a Pt catalyst to form a pressure-sensitive adhesive having excellent peel strength at a high temperature. U.S. Patent No. 0,172,140 A1 describes the high viscosity and high folding shear strength catalyzed by the addition of a hydroxyl group-containing polydimethylsiloxane gum and a hydroxyl group-containing MQ resin (M:Q less than 1.1:1). And a wide range of peel strength pressure sensitive adhesives. There are other patents which describe the mixing of alkenyl and hydroxy containing polysiloxanes as part of a pressure sensitive adhesive by some means, as described in U.S. Patent Publication No. 2010/0168313 A1, the one end of which is hydroxy and the other Alkenyl-terminated polysiloxanes (hydroxyl-terminated polysiloxanes, condensation of hydrogen-containing silicone resins and catalysts), alkenyl-terminated polysiloxanes, and silicone resins, cured by Pt A pressure sensitive adhesive which also has excellent tack and good peel strength at high temperatures. Further, as described in U.S. Patent No. 7,768,591, a solvent-free pressure-sensitive adhesive is prepared using an alkenyl group-containing polysiloxane and a hydroxyl group-containing MQ resin, a diluent, a hydrogen-containing crosslinking agent, a Pt catalyst, and an inhibitor. The pressure sensitive adhesive has excellent bonding strength at high temperatures. For example, U.S. Patent No. 6,387,487 describes the excellent adhesion of a vinyl-terminated polysiloxane, a hydroxyl-terminated polysiloxane, and a silicone resin to a high temperature by curing two vulcanizing agents (addition molding and an organic vulcanizing agent). A low-pressure pressure-sensitive adhesive of strength.

technical problem

The technical problem to be solved by the present invention is to provide a solvent-free silicone pressure-sensitive adhesive which has good initial tack, long-lasting property, suitable peel strength and drug release property, and can be repeatedly used, and a preparation method thereof. Solve the problem that the initial pressure-sensitive adhesive has poor initial tack and peel strength, and can not be used repeatedly.

Technical solution

A technical solution to solve the technical problem of the present invention is to provide a solvent-free silicone pressure-sensitive adhesive, and the composition of the silicone pressure-sensitive adhesive includes:

100 parts by mass of an alkenyl group-containing polydimethylsiloxane;

1 to 300 parts by mass of a polydimethylsiloxane having a hydroxyl group;

1 to 50 parts by mass of MQ resin;

1 to 30 parts by mass of polyisobutylene;

20 to 200 parts by mass of a diluent;

0.01 to 10 parts by mass of a crosslinking agent;

A platinum catalyst that cures the pressure sensitive adhesive.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the alkenyl group-containing polydimethylsiloxane has a viscosity of 500 to 50,000 mPa•s at 25 °C.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the viscosity of the polydimethylsiloxane having a hydroxyl group at a terminal group of 50 to 5,000 at 25 ° C mPa•s. The hydroxy-terminated polydimethylsiloxane may be any of hydroxy-terminated methylsiloxane, methylvinylsiloxane or methylvinylphenylsiloxane.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the MQ resin is composed of R ₃ SiO _1/2 (M group) and SiO _4/2 (Q group), and the molar ratio of M/Q is 0.6. : 1 to 1.9:1, R is a monovalent hydrocarbon having 1 to 20 carbon atoms.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the polyisobutylene has a molecular weight of from 350 to 3,500.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the diluent is a silicone oil having a viscosity of 50 to 10,000 mPa•s at 25 °C.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the crosslinking agent is an organohydrogenpolysiloxane having at least two Si-H groups in the molecule.

As a further improvement of the silicone pressure-sensitive adhesive of the present invention, the platinum catalyst is treated platinum, platinum black, chloroplatinic acid, ethanol-modified chloroplatinic acid, chloroplatinic acid/olefin complex, chloroplatinic acid/ An olefin siloxane complex or a chloroplatinic acid/divinyltetramethyldisiloxane complex.

And, a method for preparing a silicone pressure-sensitive adhesive, the method comprising the steps of:

Step 1: Preparation of MQ resin

100 parts by mass of water, 40 to 80 parts by mass of hydrochloric acid, 20 to 80 parts by mass of ethanol, 5 to 25 parts by mass of a vinyl blocking agent, and 100 to 180 parts by mass of hexamethyldisiloxane are put into In the three-necked flask, stir stirring and control the temperature at 70 °C. Water bath heating 30 After min, 300-500 parts by mass of tetraethyl orthosilicate was slowly added dropwise, the dropping time was controlled to be greater than 1 h, and the temperature was controlled at 73 ± 2 °C. After the completion of the dropwise addition, stirring was continued for 1 hour for cohydrolysis. Then, the heating and stirring were stopped, and the reacted solution was poured into a separatory funnel to stand for stratification, and the lower aqueous solution was separated. The upper layer solution is washed to a neutral pH, heated to 120 ° C, and the organic solution is distilled, and vacuumed to distill off most of the solvent to obtain a higher viscosity MQ resin, which is diluted with a vinyl silicone oil to a viscosity of 80,000 to 100,000. mPa•s.

Step 2: 100 parts by mass of an alkenyl group-containing polydimethylsiloxane, 1 to 300 parts by mass of a hydroxyl group-terminated polydimethylsiloxane, and 1 to 50 parts by mass. The obtained MQ resin, 1 to 30 parts by mass of polyisobutylene, and 20 to 200 parts by mass of a diluent are mixed and uniformly stirred to obtain a base rubber.

Step 3: The base rubber prepared in the second step is divided into first and second aliquots, 0.01 to 1 part of a platinum catalyst is added to the first portion and mixed, and 0.01 to 10 parts of cross-linking is added to the second portion. And 0.0001 to 0.01 parts by mass of the inhibitor and mix; then the first and second portions are uniformly mixed and cured at 150 ° C. 3 In minutes, a solvent-free silicone pressure sensitive adhesive was obtained.

In the method of the present invention, in the third step, the inhibitor is 1-ethynyl-cyclohexanol, 3-methyl-1-penten-3-ol or benzotriazole.

Beneficial effect

Compared with the prior art, the beneficial technical effects of the present invention are:

1. The present invention uses a polyhydroxysiloxane having a terminal hydroxyl group and a polydimethylsiloxane having a vinyl group to be mixed or mixed, thereby reducing or eliminating polydimethylsiloxane in a platinum catalytic system. The bubbles generated by the addition of oxyalkylene (hydroxyl capping), at the same time, the two polysiloxanes have similar functional groups to the MQ resin, and can have better compatibility therewith.

2. Use MQ resin containing hydroxyl and vinyl. The introduction of the hydroxyl group provides suitable adhesion and bond strength between the pressure sensitive adhesive and the substrate. The introduction of vinyl can improve the curing properties of the pressure-sensitive adhesive and adjust the adhesion to the substrate.

3. Add polyisobutylene. Due to the unique lattice structure formed by the distortion of long-chain macromolecules of polyisobutylene, it has good compatibility with western medicine or traditional Chinese medicine, no allergies, repeated tearing, non-sticky hair and high temperature and no overflow rubber. The addition of a moderate amount of high-concentration polyisobutylene can enhance the cohesive force of the pressure-sensitive adhesive, thereby ensuring good long-term performance and high peel strength of the pressure-sensitive adhesive, while avoiding sticking and the like.

4. Adjustable diluent viscosity and dosage. It can make a wide range of use between the pressure-sensitive adhesive prepared and the substrate.

5. In the present invention, a hydrogen-containing crosslinking agent having a low degree of polymerization is used, which has an excellent chain extension reaction when reacted with an alkenyl group, and increases the toughness and other mechanical properties of the pressure-sensitive adhesive.

Embodiments of the invention

The invention provides a solventless type silicone pressure sensitive adhesive and a preparation method thereof. The pressure-sensitive adhesive is mixed or mixed with a hydroxyl group-terminated polydimethylsiloxane and a vinyl group-containing polydimethylsiloxane, and a polyhydroxybutyl group-containing MQ resin is used to add polyisobutylene. A low degree of polymerization of a hydrogen-containing crosslinking agent is used. The silicone pressure-sensitive adhesive prepared by the invention has good initial tack, long-lasting effect, suitable peel strength and drug release property, can be repeatedly used, and can be used for pressure-sensitive adhesive tape and medical pressure-sensitive adhesive tape ( It can be accompanied by Chinese herbal medicines, as well as other functional materials that require such pressure sensitive properties.

The composition of the silicone pressure sensitive adhesive includes:

Component A: 100 parts by mass of an alkenyl group-containing polydimethylsiloxane;

Component B: 1 to 300 parts by mass of a polydimethylsiloxane whose terminal group is a hydroxyl group;

Component C: 1 to 50 parts by mass of MQ resin;

Component D: 1 to 30 parts by mass of polyisobutylene;

Component E: 20 to 200 parts by mass of a diluent;

Component F: 0.1 to 5 parts by mass of a crosslinking agent;

Ingredient G: A platinum catalyst capable of curing a pressure sensitive adhesive.

Among them, the component A is a polydimethylsiloxane whose terminal group is an alkenyl group, and its molecular formula is as shown in (I).

R ² R ¹ ₂ Si O (R ¹ ₂ Si O) _m Si R ¹ ₂ R ² (I)

Wherein R ¹ is an alkyl group or an aryl group having 1 to 10 carbon atoms, an alkyl group such as a methyl group, an ethyl group or a propyl group, and an aryl group such as a phenyl group or a tolyl group. Wherein at least 99.5% of R ¹ is an alkyl group, preferably a methyl group. R ² is an alkenyl group having 1 to 10 carbon atoms, such as a vinyl group, an allyl group or a propenyl group, preferably a vinyl group. The value of m is in the range of 20 to 1200, preferably in the range of 50 to 1,000, and more preferably in the range of 60 to 600. At 25 ° C, the viscosity of component A is between 500 and 50,000 mPa•s. The mass percentage of component A in the total weight is from 20% to 80%, preferably from 20% to 60%, more preferably from 20% to 40%. Vinyl terminated polyorganosiloxanes can be prepared by some common methods for preparing polyorganosiloxanes, such as hydrolyzable siloxanes such as vinyl dimethyl chlorosiloxane and dimethyl dichloride. Siloxane) is prepared by co-hydrolysis concentration in a suitable ratio. Or using 1,3-divinyltetramethyldisiloxane (such as symmetrical divinyldimethyldiphenyldisiloxane) as the capping group of polyorganosiloxane and diorganosiloxane An alkane such as octamethylcyclotetrasiloxane is obtained by hydrolysis under an acid or base catalyst. Regardless of the method used to prepare ingredient A, a certain amount of a volatile small molecular weight polydimethylsiloxane, such as a methyl tetramer, is usually produced. The volatility of the polydimethylsiloxane adversely affects the properties of the pressure sensitive adhesive and can be removed by heat treatment or the like during the preparation process.

Component B is a polydimethylsiloxane whose terminal group is a hydroxyl group, and its molecular formula is as shown in (II).

R ¹ ₂ Si(OH) O (R ¹ ₂ SiO) _p Si R ¹ ₂ (OH) (II)

Wherein R ¹ is an alkyl group or an aryl group having 1 to 10 carbon atoms, an alkyl group such as a methyl group, an ethyl group or a propyl group, and an aryl group such as a phenyl group or a tolyl group. Wherein at least 99.5% of R ¹ is an alkyl group, preferably a methyl group. R ² is an alkenyl group having 2 to 10 carbon atoms, such as a vinyl group, an allyl group or a propenyl group, preferably a vinyl group. p is a value of from 20 to 1200, preferably from 50 to 1,000, more preferably from 60 to 600. The viscosity of component B is between 500 and 50,000 mPa•s at 25 °C. The hydroxy-terminated polydimethylsiloxane may be any of a hydroxy-terminated methylsiloxane, methylvinylsiloxane or methylvinylphenylsiloxane, vinyl and benzene. The total number of bases is from 0 to 5% of the number of silicon atoms. The amount of the component B to be added is preferably from 1 to 300 parts by mass, particularly preferably from 50 to 200 parts by mass, per 100 parts by mass of the component A.

Mixing or mixing with a hydroxyl group-terminated polydimethylsiloxane and a vinyl group-terminated polydimethylsiloxane can reduce or eliminate polydimethylsiloxane (hydroxyl group) in a platinum catalyst system. The bubbles generated by the addition of the capping), at the same time, the two siloxanes have similar functional groups to the component C (MQ resin), and can have better compatibility therewith.

Component C is an MQ resin. The MQ resin is composed of R ₃ SiO _1/2 (M group) and SiO _4/2 (Q group), and R is a monovalent group having 1 to 6 carbon atoms and contains at least 95% of an alkyl group. Group, preferably methyl. In the case of an unsaturated alkenyl group, the content of the unsaturated alkenyl group is not more than 0.5%, preferably not more than 0.1%. MQ silicone resin has a complex three-dimensional spherical structure with two different chain links, wherein the organic chain links can improve the compatibility and adhesion of silicone rubber, and the siloxane chain links can reinforce silicone rubber. The effect can improve the cohesive strength of the pressure sensitive adhesive. The M/Q molar ratio in MQ determines the molecular weight and hydroxyl content of the silicone resin, and a generally suitable M/Q ratio is between 0.6 and 0.9. When M/Q<0.6, it is easy to gel, difficult to prepare, and has poor compatibility with silicone rubber. When M/Q>0.9, the compatibility with silicone rubber is good, but the cohesive force is lowered. The hydroxyl group content affects the degree of reaction with the silicone rubber, and the adhesion and bonding strength of the pressure sensitive adhesive to the substrate, and the range is generally from 1 to 5%. By introducing comonomers containing pendant groups of different functional groups, MQ resins containing different groups such as a vinyl group, a hydrogen group, and a phenyl group can be obtained, thereby imparting special properties to the MQ resin. If a vinyl group is introduced, the curing property can be improved, and the adhesion to the substrate can be adjusted. The introduction of a phenyl group improves the heat resistance and flexibility of the silicone resin. The molar ratio of M/Q in the present invention is from 0.5:1 to 1.9:1, preferably from 0.6:1 to 1.0:1, more preferably from 0.7:1 to 0.9:1. The amount of the component C to be added is preferably from 1 to 50 parts by mass based on 100 parts by mass of the component A.

Component D is polyisobutylene. Polyisobutylene (PIB) is a generic term for homopolymer and copolymer products of isobutylene (2-methylpropene). Its chemical structure is a typical saturated linear polymer. The whole structure is mainly composed of the repeating unit -CH ₂ C(CH ₃ ) ₂ -, the head group is CH ₃ -, and the tail group is -CH ₂ -C (CH). ₃ ) = CH or -CH=C(CH ₃ )-CH ₃ . Due to the unique lattice structure formed by the long-chain macromolecules of PIB, it has good inclusiveness to Western medicine or traditional Chinese medicine, no allergies, repeated tearing, non-sticky hair and high temperature and no overflow. Polyisobutylene can be classified into high molecular weight polyisobutylene (molecular weight greater than 1000) and low molecular weight polyisobutylene (molecular weight less than 1000) according to its molecular weight. The addition of moderately high-concentration polyisobutylene can enhance the cohesive force of the pressure-sensitive adhesive, which can ensure its high peel strength and avoid sticking. Among the pressure-sensitive adhesives of the present invention, medium-high molecular weight polyisobutylene having a molecular weight of from 350 to 3,500 is preferred. The amount of the component D to be added is preferably from 1 to 30 parts by mass based on 100 parts by mass of the component A.

Ingredient E is a diluent. The component of the diluent is a low viscosity linear non-functional silicone oil having a molecular formula as shown in (III).

R ₃ Si O (R ₂ Si O) _n Si R ₃ (III)

Wherein R is the same or different inactive hydrocarbon group such as methyl, ethyl, propyl and phenyl, n is from 5 to 1000, and has a viscosity of from 50 to 10,000 at 25 ° C. mPa•s. Component E may be dimethyl silicone oil, diethyl silicone oil or methyl phenyl silicone oil. The amount of the component D to be added is preferably 20 to 200 parts by mass based on 100 parts by mass of the component A.

Component F is a crosslinking agent. The organohydrogenpolysiloxane containing at least two Si-H groups in the molecule is a crosslinking agent in which an addition reaction of a platinum catalyst and an alkenyl group in the base rubber can be used as a curing agent in an addition reaction. Those known organohydrogenated polysiloxanes which cure silicone rubber compositions. It can be linear, circular or branched. Typically, it has the structural formula (IV):

The average composition shown:

R ¹ _x H _y Si O _(4-xy)/2 (IV)

Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, including alkyl, aryl and aralkyl groups and halogens and cyano groups thereof The form is substituted and preferably does not contain an aliphatic unsaturated bond. x and y are positive numbers satisfying 1 ≤ x ≤ 2.2, 0.002 ≤ y ≤ 1, and 1.002 ≤ x + y ≤ 3. In the molecule, preferably at least two, preferably at least three Si-H groups are present and may be located at the end of the molecular chain or at any intermediate position. The organopolysiloxane containing a Si—H bond may be a trimethylsiloxy-terminated methyl hydrogen-containing polysiloxane, a trimethylsiloxy-terminated methyl hydrogen-containing polysiloxane, and a dimethyl group. A polymer of siloxane, a polymer of dimethylhydrosilyloxy-terminated methylhydrogenpolysiloxane and dimethylsiloxane, tetramethyltetrahydrocyclotetrasiloxane or the like.

The organohydrogenated polysiloxane preferably has a ratio of 300 or less at 25 ° C or lower. The viscosity of mPa·s is 0.01 to 10 parts by mass based on 100 parts by mass of the component A, and the organohydrogenpolysiloxane is mixed. Preferably, the organohydrogenpolysiloxane is used in an amount such that each alkenyl group in the component A obtains from 0.05 to 10, more preferably from 1 to 4, silicon-bonded hydrogen atoms. If the number of silicon-bonded hydrogen atoms is less than 0.05, cross-linking may be insufficient and satisfactory mechanical strength may not be obtained. If the number of hydrogen atoms is more than 10, the cured product may have poor physical properties. Further, it is also preferred to add a known platinum catalyst inhibitor such as a polymethylvinylsiloxane cyclic compound, an acetylenic alcohol, and a peroxide to the pressure-sensitive adhesive.

Component G is a platinum catalyst. The platinum catalyst may be treated platinum, platinum black, chloroplatinic acid, ethanol modified chloroplatinic acid, chloroplatinic acid/olefin complex, chloroplatinic acid/olefin siloxane complex, chloroplatinic acid/two Vinyl tetramethyldisiloxane complex. Preferably, the mass content of the metal platinum in the component G is 0.1 to 500. Ppm. In order to adjust the catalytic activity of the platinum catalyst, some auxiliaries such as 1-ethynyl-cyclohexanol, 3-methyl-1-penten-3-ol or benzotriazole may be added.

The pressure sensitive adhesive of the present invention may comprise one or more additives. For example, a dye or pigment may be added as a colorant; a conductive and/or thermally conductive compound may be added to make the adhesive conductive and/or thermally or antistatic; an antioxidant or a bacterial inhibitor may be added; a UV stabilizer and absorption may be added. Agents, such as hindered amine light stabilizers (HALS), are used to stabilize the PSA from UV degradation and to block specific UV wavelengths from passing through the article. Other additives include adhesion promoters, fillers, tackifiers, glass or ceramic microbubbles, expanded and non-expanded polymeric microspheres, blowing agents, polymers and other modifiers such as clays, flame retardants and Compatibilizer. These additives may be at about 0.05 based on the total weight of the pressure sensitive adhesive. Wt% ~ about 3 The wt% is used in various combinations in a range of amounts. The pressure sensitive adhesive can be applied to a suitable release liner by a number of methods including solution coating, solution spraying, hot melt coating, extrusion, coextrusion, lamination, and printing. Or applied directly to a substrate (eg, a tape backing) to form an adhesive laminate.

The invention also provides a preparation method of a pressure sensitive adhesive, the preparation method comprising the following steps:

Step 1: Preparation of MQ resin.

Because MQ silicone resin has a complex three-dimensional spherical structure, it has two kinds of identical chain links, wherein the organic chain links can improve the compatibility with silicone rubber and enhance the viscosity. The siloxane chain links have silicone rubber. The reinforcing effect can improve the cohesive strength of the pressure sensitive adhesive. MQ silicone resin is the main component of silicone pressure-sensitive adhesive. The main factors affecting the performance of silicone pressure-sensitive adhesive are: (1) M/Q ratio: it determines the molecular weight and hydroxyl content of silicone resin. Generally, it is suitable for M/. The Q ratio is between 0.6 and 0.9, M/Q is less than 0.6, it is easy to gel, and it is difficult to prepare, and has poor compatibility with silicone rubber. M/Q>0.9, good compatibility with silicone rubber, but reduced cohesion. (2) Hydroxyl content: It affects the degree of reaction with the silicone rubber, and the adhesion and bonding strength of the pressure-sensitive adhesive to the substrate. The range is generally from 1 to 5%. (3) Functional group content: By introducing a comonomer having a side group containing a different functional group, an MQ resin containing a different group such as a vinyl group, a hydrogen group or a phenyl group can be obtained, thereby imparting special properties to the MQ resin. If a vinyl group is introduced, the curing property can be improved, and the adhesion to the substrate can be adjusted; and the introduction of a phenyl group can improve the heat resistance and flexibility of the silicone resin.

Step 2: 100 parts by mass of an alkenyl group-containing polydimethylsiloxane, 1 to 300 parts by mass of a hydroxyl group-terminated polydimethylsiloxane, and 1 to 50 parts by mass. The obtained MQ resin, 1 to 30 parts by mass of polyisobutylene, and 20 to 200 parts by mass of a diluent are mixed and uniformly stirred to obtain a base rubber. Then, it is divided into first and second aliquots, 0.01 to 1 part of a platinum catalyst is added to the first portion and mixed, and 0.01 to 10 parts of a crosslinking agent is added to the second portion and mixed.

Step 3: The first and second portions of the second step are uniformly mixed and cured at 150 ° C for 3 minutes to obtain a solvent-free pressure-sensitive adhesive.

The invention has the following advantages:

1. The present invention uses a polyhydroxysiloxane having a terminal hydroxyl group and a polydimethylsiloxane having a vinyl group to be mixed or mixed, thereby reducing or eliminating polydimethylsiloxane in a platinum catalytic system. The bubbles generated by the addition of oxyalkylene (hydroxyl capping), at the same time, the two siloxanes have similar functional groups to the MQ resin, and can have better compatibility with them.

2. Use MQ resin containing hydroxyl and vinyl. The introduction of the hydroxyl group provides suitable adhesion and bond strength between the pressure sensitive adhesive and the substrate. The introduction of vinyl improves the curing properties of the pressure sensitive adhesive and adjusts the adhesion to the substrate.

3. Add polyisobutylene. Due to the unique lattice structure formed by the distortion of long-chain macromolecules of polyisobutylene, it has good inclusiveness to western medicine or traditional Chinese medicine, no allergies, repeated tearing, non-sticky hair and high temperature and no gelation. The addition of a moderate amount of high-concentration polyisobutylene can enhance the cohesive force of the pressure-sensitive adhesive, thereby ensuring good long-term performance and high peel strength of the pressure-sensitive adhesive, while avoiding sticking and the like.

Therefore, the solvent-free silicone pressure-sensitive adhesive of the present invention is a silicone pressure-sensitive adhesive having good initial tack, long-acting property, suitable peel strength and drug release property, and at the same time, it is non-toxic and environmentally friendly. Can be used repeatedly. Therefore, the pressure-sensitive adhesive of the present invention can be made into a pressure-sensitive adhesive tape, a medical pressure-sensitive adhesive tape (with a Chinese herbal medicine), and other functional materials requiring such pressure-sensitive properties.

The invention will now be further described in connection with a number of specific embodiments. In the examples, "parts" means "parts by mass".

Related embodiment

100 parts of water, 60 parts of hydrochloric acid, 52 parts of ethanol, 15 parts of vinyl blocking agent and 142 parts of hexamethyldisiloxane were placed in a three-necked flask, and stirring was started to control the temperature at 70 ° C. Water bath heating 30 After min, 400 parts of ethyl orthosilicate was slowly added dropwise, the dropping time was controlled to be greater than 1 h, and the temperature was controlled at 73 ± 2 ° C. After the completion of the dropwise addition, stirring was continued for 1 h for cohydrolysis. Heating and stirring were stopped, and the reacted solution was poured into a separatory funnel to stand for stratification, and the lower aqueous solution was separated. The upper layer solution was washed with water until the pH was neutral, heated to 120 ° C, and the organic solution was distilled, and vacuumed to distill off most of the solvent to obtain a higher viscosity MQ resin. Dilute with vinyl silicone oil to a viscosity of 80,000 to 100,000 mPa•s.

Example 1

100 parts of polydimethylsiloxane having a terminal group of vinyl groups (viscosity of 1000 mPa•s) and 75 parts (about 20.5) Twt%) polydimethylsiloxane having a hydroxyl group end group (viscosity: 1200 mPa•s), 25 parts of MQ resin obtained in the related examples, and 15 parts of polyisobutylene (viscosity: 1200) mPa•s) and 150 parts of dimethyl silicone oil (viscosity of 500 mPa•s) were mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst to A (Square Silicone CA28, platinum content 2000 ppm) and mix, add 3 parts of hydrogen-containing silicone oil to B part (hydrogen content is 0.25) Wt%) and 0.001 parts of the inhibitor and mix. Mix A and B separately and cure at 150 °C. 3 Minutes (min), a pressure sensitive adhesive was obtained. The pressure-sensitive adhesive has good viscosity, fine and uniform micro-pores, soft rubber after curing, and good peel strength. After the pressure-sensitive adhesive was left for 6 months, the viscosity was substantially unchanged.

Example 2

The same procedure as in Example 1 was carried out except that no MQ resin was added. The pressure-sensitive adhesive prepared in this manner has poor adhesion and is obviously debonded after being left for 3 days.

Example 3

The same procedure as in Example 1 was carried out except that no hydroxypolysiloxane was added. The pressure-sensitive adhesive prepared in this manner has poor adhesion and is obviously debonded after being left for 3 days.

Example 4

The same procedure as in Example 1 was carried out except that no polyisobutylene was added. The pressure-sensitive adhesive prepared in this manner has poor adhesion and is obviously debonded after being left for 3 days.

Example 5

100 parts of a polydimethylsiloxane having a vinyl group end group (viscosity of 1000) mPa•s), 75 parts of hydroxyl-terminated polydimethylsiloxane (viscosity of 1200 mPa•s) and 150 parts of dimethicone (viscosity of 500) mPa•s) is mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst in A (Square Silicone CA28, platinum content 2000 Ppm) and mix, add 3 parts of hydrogen-containing silicone oil (hydrogen content of 0.25 wt%) and 0.001 parts of inhibitor to the B part and mix. Mix A and B separately and cure at 150 °C. 3 Min, a pressure sensitive adhesive is obtained. This pressure-sensitive adhesive has good adhesion and good peel strength, but after 15 days of standing, the viscosity gradually decreases.

Example 6

100 parts of a polydimethylsiloxane having a vinyl group end group (viscosity of 1000) mPa•s), 25 parts of MQ resin obtained in the relevant examples and 150 parts of dimethicone (viscosity of 500) mPa•s) is mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst in A (Square Silicone CA28, platinum content 2000 Ppm) and mix, add 3 parts of hydrogen-containing silicone oil (hydrogen content of 0.25 wt%) and 0.001 parts of inhibitor to the B part and mix. Mix A and B separately and cure at 150 °C. 3 Min, a pressure sensitive adhesive is obtained. This pressure-sensitive adhesive has good adhesion and good peel strength, but after 15 days of standing, the viscosity gradually decreases.

Example 7

100 parts of polydimethylsiloxane having a terminal group of vinyl (viscosity of 1000 mPa•s) and 50 parts (less than 20) Twt%) polydimethylsiloxane having a hydroxyl group end group (viscosity: 1200 mPa•s), 25 parts of MQ resin obtained in the related examples, and 15 parts of polyisobutylene (viscosity: 1200) mPa•s) and 150 parts of dimethyl silicone oil (viscosity of 500 mPa•s) were mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst to A (Square Silicone CA28, platinum content 2000 ppm) and mix, add 3 parts of hydrogen-containing silicone oil to B part (hydrogen content is 0.25 wt %) and 0.001 parts of the inhibitor and mix. The parts A and B were uniformly mixed and cured at 150 ° C for 3 minutes to obtain a pressure-sensitive adhesive. This pressure-sensitive adhesive contains less air bubbles, has higher viscosity, and has higher peel strength.

Example 8

100 parts of polydimethylsiloxane having a terminal group of vinyl (viscosity of 1000 mPa•s) and 290 parts (about 50) Twt%) polydimethylsiloxane having a hydroxyl group end group (viscosity: 1200 mPa•s), 25 parts of MQ resin obtained in the related examples, and 15 parts of polyisobutylene (viscosity: 1200) mPa•s) and 150 parts of dimethyl silicone oil (viscosity of 500 mPa•s) were mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst to A (Square Silicone CA28, platinum content 2000 ppm) and mix, add 3 parts of hydrogen-containing silicone oil to B part (hydrogen content is 0.25 wt %) and 0.001 parts of the inhibitor and mix. The parts A and B were uniformly mixed and cured at 150 ° C for 3 minutes to obtain a pressure-sensitive adhesive. This pressure-sensitive adhesive contains more bubbles, has lower viscosity, and has lower peel strength.

Example 9

100 parts of vinyl dimethicone (viscosity 1000 mPa•s), 350 parts (greater than 50) Twt%) polydimethylsiloxane having a hydroxyl group end group (viscosity: 1200 mPa•s), 25 parts of MQ resin obtained in the related examples, and 15 parts of polyisobutylene (viscosity: 1200) mPa•s) and 150 parts of dimethyl silicone oil (viscosity of 500 mPa•s) were mixed and stirred to obtain a base rubber. Then divide it into two equal parts A and B, and add 0.6 part of platinum catalyst to A (Square Silicone CA28, platinum content 2000 ppm) and mix, add 3 parts of hydrogen-containing silicone oil to B part (hydrogen content is 0.25 wt %) and 0.001 parts of the inhibitor and mix. The parts A and B were uniformly mixed and cured at 150 ° C for 3 minutes to obtain a pressure-sensitive adhesive. This pressure-sensitive adhesive contains more bubbles, has lower viscosity, and has lower peel strength.

From the above, in the pressure-sensitive adhesive of the present invention, the introduction of polyisobutylene can maintain the long-term effect of the pressure-sensitive adhesive. At the same time, when the content of hydroxypolysiloxane is less than 20 When wt%, the pressure sensitive adhesive contains less bubbles, higher viscosity, higher peel strength; when the content of hydroxypolysiloxane is not less than 50 When wt%, the obtained pressure-sensitive adhesive contains more bubbles, lower viscosity and lower peel strength; when the content of hydroxypolysiloxane is 20 When the wt% is about, the pressure-sensitive adhesive has fine and uniform micro-pores, the rubber is soft, and the pressure-sensitive adhesive has the best adhesion effect.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

A solvent-free silicone pressure-sensitive adhesive characterized in that the composition of the silicone pressure-sensitive adhesive comprises:

100 parts by mass of an alkenyl group-containing polydimethylsiloxane;

1 to 300 parts by mass of a polydimethylsiloxane having a hydroxyl group;

1 to 50 parts by mass of MQ resin;

1 to 30 parts by mass of polyisobutylene;

20 to 200 parts by mass of a diluent;

0.1 to 5 parts by mass of a crosslinking agent;

A platinum catalyst that cures the pressure sensitive adhesive.
The silicone pressure-sensitive adhesive according to claim 1, wherein the terminal group is an alkenyl group-containing polydimethylsiloxane having a viscosity of 500 to 50,000 at 25 °C. mPa•s.
The silicone pressure-sensitive adhesive according to claim 1, wherein the polydimethylsiloxane having a hydroxyl group at the terminal group has a viscosity of 50 to 5,000 at 25 °C. mPa•s.
The silicone pressure-sensitive adhesive according to claim 1, wherein said MQ resin is composed of a R 3 SiO 1/2 group and a SiO 4/2 group, an R 3 SiO 1/2 group and SiO. The molar ratio of the 4/2 group is from 0.6:1 to 1.9:1.
The silicone pressure-sensitive adhesive according to claim 1, wherein the polyisobutylene has a molecular weight of from 350 to 3,500.
The silicone pressure-sensitive adhesive according to claim 1, wherein the diluent is a silicone oil having a viscosity of 50 to 1,000 at 25 ° C. mPa•s.
The silicone pressure-sensitive adhesive according to claim 1, wherein the crosslinking agent is an organohydrogenpolysiloxane having at least two Si-H groups in the molecule.
The silicone pressure-sensitive adhesive according to claim 1, wherein the platinum catalyst is treated platinum, platinum black, chloroplatinic acid, ethanol-modified chloroplatinic acid, chloroplatinic acid/olefin complex. A chloroplatinic acid/olefin siloxane complex or a chloroplatinic acid/divinyltetramethyldisiloxane complex.
A method for preparing a silicone pressure-sensitive adhesive, characterized in that the preparation method comprises the following steps:

Step 1: preparing MQ resin;

Step 2: 100 parts by mass of an alkenyl group-containing polydimethylsiloxane, 1 to 300 parts by mass of a hydroxyl group-terminated polydimethylsiloxane, and 1 to 50 parts by mass. The obtained MQ resin, 1 to 30 parts by mass of polyisobutylene and 20 to 200 parts by mass of a diluent are mixed and uniformly stirred to obtain a base rubber;

Step 3: The base rubber prepared in the second step is divided into first and second aliquots, 0.01 to 1 part of a platinum catalyst is added to the first portion and mixed, and 0.01 to 10 parts of cross-linking is added to the second portion. The agent and 0.0001 to 0.01 parts by mass of the inhibitor are mixed, and then the first part and the second part are uniformly mixed and cured at 150 ° C for 3 minutes to obtain a solventless type silicone pressure sensitive adhesive.
The method for preparing a silicone pressure-sensitive adhesive according to claim 9, wherein in the third step, the inhibitor is 1-ethynyl-cyclohexanol or 3-methyl-1-pentene. 3-ol or benzotriazole.