Adhesive compositions and adhesives

Abstract

This will diversify the options for adhesives whose adhesive strength can be altered by light irradiation. [Solution] The adhesive composition comprises a modified cinnamic acid monomer which is an esterified product of a reaction component containing cinnamic acid, hydroxyethyl methacrylate, and a catalyst, a propylene glycol methyl ether acrylate monomer, an initiator, and a solvent containing butyl acetate.

Description

Technical Field

[0001] The present invention relates to an adhesive, and more particularly, to an adhesive composition and an adhesive.

Background Art

[0002] In the manufacturing process of electronic products, a photocurable adhesive is often used as a temporary fixing agent for fixing objects to each other. Existing photocurable adhesives separate objects joined by the photocurable adhesive by irradiating light of a specific wavelength to reduce the adhesive force. However, a problem with such photocurable adhesives is that there is no way to restore the adhesive force before irradiation after light irradiation, so they cannot be reused. Therefore, how to restore the adhesive force before irradiation and make it reusable after irradiating light of a specific wavelength has become a major focus in the development of this type of photocurable adhesive.

[0003] Taiwan Patent Application Publication No. 201819349 (Patent Document 1) discloses an adhesive whose adhesive force can be repeatedly changed by light irradiation. Under light irradiation with a wavelength of 200 nm to 280 nm, this adhesive has a strong adhesive force due to the polymerization of cinnamic acid monomer and monomer A. Under light irradiation with a wavelength of 280 nm to 400 nm, a reversible cyclization reaction occurs between the first unsaturated bond sites adjacent to two benzene rings each derived from the cinnamic acid monomer structure of the adhesive, and the adhesive force decreases. Among them, monomer A includes a polyurethane monomer structure or an acrylic monomer structure, and the acrylic monomer structure is selected from propylene glycol methyl ether acrylate (OBA), butyl acrylate (BA), methyl methacrylate (MMA), ethylhexyl acrylate (EHA), glycidyl methacrylate (GMA) or acrylic acid (AA).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Given the wide range of applications for adhesives whose adhesive strength can be altered by light irradiation, the inventors of this invention believe it is necessary to focus on developing various new products for the market and diversify the options available, and this was the objective of the present invention. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides an adhesive composition comprising a modified cinnamic acid monomer which is an esterified product of a reaction component comprising cinnamic acid, hydroxyethyl methacrylate, and a catalyst; a propylene glycol methyl ether acrylate monomer; an initiator; and a solvent containing butyl acetate.

[0007] Furthermore, as a means to achieve the above objective, the present invention provides an adhesive which is a crosslinking reaction product of the above adhesive composition and comprises a modified cinnamic acid monomer structural unit represented by the following chemical formula (3) and a propylene glycol methyl ether acrylate monomer structural unit represented by the chemical formula (4).

[0008] [ka]

[0009] [ka] [Effects of the Invention]

[0010] The adhesive composition of the present invention combines a modified cinnamic acid monomer with a propylene glycol methyl ether acrylate monomer, thereby producing an adhesive whose adhesive strength changes when irradiated with different light sources. Therefore, the adhesive of the present invention can be used repeatedly to bond or separate two objects from each other. [Modes for carrying out the invention]

[0011] <Adhesive composition> In one embodiment, the adhesive composition of the present invention comprises a modified cinnamic acid monomer, a propylene glycol methyl ether acrylate monomer, an initiator, and a solvent.

[0012] The modified cinnamic acid monomer described above is formed by esterifying a reaction component containing cinnamic acid, hydroxyethyl methacrylate (abbreviated as HEMA), and a catalyst; in other words, it is an esterified product of the above reaction component. The type of catalyst is not particularly limited, and any reagent capable of causing an esterification reaction between cinnamic acid and HEMA can be used in the present invention, one example being dioctyltin(IV) dilaurate. In some examples, the catalyst is dioctyltin(IV) dilaurate. In some examples, the modified cinnamic acid monomer has the structure of the following chemical formula (1).

[0013] [ka]

[0014] In some embodiments, the reaction component further comprises a solvent. Examples of solvents for this reaction component include, but are not limited to, propylene glycol methyl ether acetate. In some examples, the solvent for the reaction component is propylene glycol methyl ether acetate.

[0015] The above propylene glycol methyl ether acrylate monomer has the structure of the following chemical formula (2).

[0016] [Chemical formula]

[0017] The above initiator is used to form an adhesive by crosslinking a modified cinnamic acid monomer and a propylene glycol methyl ether acrylate monomer. There is no particular limitation on its type, and various reagents can be used in the present invention as long as the above effects can be obtained. In some embodiments, the initiator is at least one selected from the group consisting of a thermal initiator and a photoinitiator. In some examples, the initiator is a thermal initiator. The thermal initiator is, for example, 2,2'-azobis(isobutyric acid methyl) (abbreviation: MAIB), but is not limited thereto. In some examples, the thermal initiator is 2,2'-azobis(isobutyric acid methyl).

[0018] The solvent in the adhesive composition contains butyl acetate. Also, in some embodiments, the solvent in the adhesive composition contains butyl acetate and propylene glycol methyl ether acetate. In the solvent in the adhesive composition, when it contains both butyl acetate and propylene glycol methyl ether acetate, the dosage of butyl acetate is more than that of propylene glycol methyl ether acetate. For example, the dosage ratio of butyl acetate to propylene glycol methyl ether acetate is 2:1. In addition, when the solvent in the adhesive composition contains both butyl acetate and propylene glycol methyl ether acetate, by making the dosage of butyl acetate more than that of propylene glycol methyl ether acetate, for example, the glass transition temperature of the product after the chemical reaction can be controlled to be -30°C to -80°C, and thus it can contribute to the control of the adhesive strength of the adhesive produced by the adhesive composition.

[0019] In some embodiments, if the dose of modified cinnamic acid monomer is 100 parts by weight, the dose of propylene glycol methyl ether acrylate monomer is in the range of 100 to 2000 parts by weight, and the dose of initiator is in the range of 4 to 6 parts by weight. In some embodiments, if the total dose of modified cinnamic acid monomer, propylene glycol methyl ether acrylate monomer, and initiator is 100 wt%, then the dose of modified cinnamic acid monomer is in the range of 4.9 wt% to 9.9 wt%, the dose of propylene glycol methyl ether acrylate monomer is in the range of 90 wt% to 95 wt%, and the dose of initiator is in the range of 0.1 wt% to 0.5 wt%.

[0020] Furthermore, in some embodiments, when the total amount of the adhesive composition is 100 wt%, the sum of the amounts of the modified cinnamic acid monomer, propylene glycol methyl ether acrylate monomer, and initiator is in the range of 30 wt% to 60 wt%, and the amount of solvent is in the range of 40 wt% to 70 wt%.

[0021] In some embodiments, the adhesive composition further comprises one acrylic monomer selected from the group consisting of 2-hydroxyethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. In some examples, the acrylic monomer is 2-ethylhexyl acrylate, which makes it possible to set the glass transition temperature of the adhesive produced by the adhesive composition to -60°C.

[0022] In some embodiments in which the adhesive composition further comprises an acrylic monomer, if the total amount of modified cinnamic acid monomer, propylene glycol methyl ether acrylate monomer, acrylic monomer, and initiator is 100 wt%, then the amount of modified cinnamic acid monomer is in the range of 4.9 wt% to 9.9 wt%, the total amount of propylene glycol methyl ether acrylate monomer and acrylic monomer is in the range of 90 wt% to 95 wt%, and the amount of initiator is in the range of 0.1 wt% to 0.5 wt%. Furthermore, in some embodiments in which the adhesive composition further comprises acrylic monomers, if the total amount of the adhesive composition is 100 wt%, the sum of the amounts of modified cinnamic acid monomer, propylene glycol methyl ether acrylate monomer, acrylic monomer, and initiator is in the range of 30 wt% to 60 wt%, and the amount of solvent is in the range of 40 wt% to 70 wt%.

[0023] <Adhesive> The present invention also provides an adhesive formed by crosslinking the above-mentioned adhesive composition, i.e., an adhesive that is a crosslinking reaction product of the above-mentioned adhesive composition. The adhesive comprises a modified cinnamic acid monomer structural unit represented by the following chemical formula (3) and a propylene glycol methyl ether acrylate monomer structural unit represented by the chemical formula (4). In some embodiments, the adhesive further comprises an acrylic monomer structural unit such as that represented by the chemical formula (5), thereby effectively controlling the glass transition temperature of the adhesive.

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] In chemical formula (5), R 1 It is selected from the group consisting of -CH2CH2OH, -CH2CH(CH2CH3)CH2CH2CH2CH3, and -CH2CH2CH2CH3.

[0028] In some embodiments, the adhesive has a structure represented by the following chemical formula (6). In some embodiments, the adhesive composition further comprises an acrylic monomer, and the adhesive has a structure represented by the following chemical formula (7). In chemical formula (7), R 1 It is selected from the group consisting of -CH2CH2OH, -CH2CH(CH2CH3)CH2CH2CH2CH3, and -CH2CH2CH2CH3. Note that in chemical formula (7), the order of arrangement of the modified cinnamic acid monomer structural unit, the propylene glycol methyl ether acrylate monomer structural unit, and the acrylic monomer structural unit can be arbitrarily changed. In some examples, when the acrylic monomer in the adhesive composition is 2-hydroxyethyl acrylate, R in chemical formula (5) 1 R is -CH2CH2OH, and the adhesive has the structure shown in the following chemical formula (7-1). In some embodiments, when the acrylic monomer in the adhesive composition is butyl acrylate, R in chemical formula (5) 1 The compound is -CH2CH2CH2CH3, and the adhesive has the structure shown in the following formula (7-2).

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] In chemical formulas (6), (7), (7-1), and (7-2), m, n, and p represent the ratio of the number of acrylic monomer structural units, propylene glycol methyl ether acrylate monomer structural units, and modified cinnamic acid monomer structural units, respectively. In chemical formulas (6), (7), (7-1), and (7-2), the numerical relationship between m, n, and p is m > n > p. The glass transition temperature of the manufactured adhesive can be controlled by adjusting the ratio of the number of m, n, and p.

[0034] In some embodiments, the adhesive has a glass transition temperature in the range of -40°C to -60°C, which allows the adhesive to have good adhesion. In some examples, the glass transition temperature of the adhesive is -40°C. In some examples, the glass transition temperature of the adhesive is -60°C, where the acrylic monomer in the adhesive composition is 2-ethylhexyl acrylate.

[0035] <Manufacturing method> The method for producing the adhesive of the present invention is described below. In some embodiments, a modified cinnamic acid monomer, a propylene glycol methyl ether acrylate monomer, an initiator, and a solvent are mixed to form an adhesive composition, and then the adhesive composition is subjected to a crosslinking reaction to produce the adhesive. In some embodiments, a modified cinnamic acid monomer, a propylene glycol methyl ether acrylate monomer, an acrylic monomer, an initiator, and a solvent are mixed to form an adhesive composition, and then the adhesive composition is subjected to a crosslinking reaction to produce the adhesive. Note that the adhesive obtained by the crosslinking reaction contains residual solvent from the adhesive composition.

[0036] When the above adhesive is irradiated with a first light source, a photocyclization reaction occurs between the first (i.e., the first from the benzene ring) unsaturated bond sites adjacent to the benzene ring of each of the two modified cinnamic acid monomer structural units in the adhesive, forming a cyclized structure. For example, this cyclized state is shown by the following chemical formula (8). The cyclized state increases the cohesive force of the adhesive, and as a result, can decrease the adhesive strength of the adhesive. Furthermore, when the adhesive is irradiated with a second light source, the above cyclized structure in the adhesive undergoes a photoring-opening reaction, becoming an open-ring state. For example, this open-ring state is shown by the chemical formula (9). The adhesive strength of the adhesive in the cyclized state is less than the adhesive strength of the adhesive in the open-ring state.

[0037] [ka]

[0038] [ka]

[0039] Note that n and p in chemical formulas (8) and (9) are the same as those explained in chemical formula (6).

[0040] In some embodiments, the first light source has a wavelength in the range of 285 nm to 295 nm, for example, 290 nm. The methyl group derived from the HEMA structure in the modified cinnamic acid monomer can cause a photocyclization reaction between the first unsaturated bonding sites adjacent to the benzene rings of each of the two modified cinnamic acid monomer structures, and the absorption peak range can be located in the range of 285 nm to 295 nm. In some embodiments, the second light source has a wavelength in the range of 220 nm to 230 nm, for example, 225 nm.

[0041] <Manufacturing Examples and Case Studies> The present invention will be further described below with reference to manufacturing examples and embodiments. However, please understand that these manufacturing examples and embodiments are merely illustrative and should not be interpreted as limitations on the implementation of the present invention.

[0042] [Production Example 1] Modified cinnamic acid monomer 10 g of cinnamic acid (manufacturer: Sigma-Aldrich, model number: 8.00235) and 8.8 g of hydroxyethyl methacrylate (abbreviated as HEMA, manufacturer: Sigma-Aldrich, model number: 8.00588) were mixed with 100 ml of propylene glycol methyl ether acetate and stirred in a 60°C water bath for 3 hours to obtain a mixture. Next, this mixture was reacted catalytically with 0.1 g of dioctyl tin(IV) dilaurate (manufacturer: Apollo Scientific Ltd., model number: APOH96F124B7, as a catalyst) for 6 hours to obtain a crude product. The crude product was then filtered by gravity using filter paper (manufacturer: ADVANTEC, model number: NO.5C) ​​to separate the filtrate containing the modified cinnamic acid monomer. The filtrate was mixed with cyclohexanone, and liquid-liquid extraction was performed using a separatory funnel to obtain the organic layer, thereby obtaining an extract containing the modified cinnamic acid monomer. Furthermore, this extract was separated and purified using a high-speed centrifuge (manufacturer: Chrom Tech, model number: MT-15000) to obtain modified cinnamic acid monomers.

[0043] The modified cinnamic acid monomer obtained in this way was analyzed by Fourier transform infrared spectroscopy (FTIR) using a Fourier transform infrared spectrometer (manufacturer: Bruker, model: VERTEX 80v). The modified cinnamic acid monomer was found to have a value of 1720 cm⁻¹. -1 An absorption peak was observed at 3453 cm², indicating that the modified cinnamic acid monomer has an ester group. Furthermore, the modified cinnamic acid monomer was found at 3453 cm². -1 The absence of an absorption peak indicates the absence of a hydroxyl group, thus confirming that the modified cinnamic acid monomer was indeed synthesized from cinnamic acid and HEMA.

[0044] Furthermore, when the modified cinnamic acid monomers obtained in this way were spectroscopically analyzed using a UV-Vis spectrophotometer (UV-vis, manufacturer: Agilent Technologies, model: CARY 300nc), the modified cinnamic acid monomers had an absorption peak at a wavelength of 290 nm, which is the absorption peak of the photocyclization reaction between the first unsaturated bond sites adjacent to the benzene rings of each of the two modified cinnamic acid monomers. The modified cinnamic acid monomers also had an absorption peak at a wavelength of 225 nm, which is the absorption peak of the photo-opening reaction of the cyclic structure after the two modified cinnamic acid monomers have undergone a photocyclization reaction to form a cyclic structure.

[0045] [Example 1] Adhesive composition and adhesive An adhesive composition was obtained by mixing 6 g of modified cinnamic acid monomer, 90 g of propylene glycol methyl ether acrylate monomer (abbreviation: OBA, manufacturer: Shiny Chemical Industrial CO., Ltd., Taiwan, model number: OBA1), and 0.3 g of 2,2'-azobis(methyl isobutyrate) (manufacturer: FUJIFILM Wako Chemicals USA, model number: V-601, used as a thermal initiator) with 66 ml of butyl acetate and 33 ml of propylene glycol methyl ether acetate. This adhesive composition was subjected to a thermal crosslinking reaction at 80°C for 6 hours to obtain an adhesive. This adhesive has the structure shown in chemical formula (6) above. In this case, n is 78 and p is 5.

[0046] [Example 2] Adhesive composition and adhesive An adhesive composition was obtained by mixing 6 g of modified cinnamic acid monomer, 10 g of propylene glycol methyl ether acrylate monomer (abbreviation: OBA, manufacturer: Shiny Chemical Industrial CO., Ltd., Taiwan, model number: OBA1), 80 g of 2-hydroxyethyl acrylate (abbreviation: 2-HEA, manufacturer: KSK, model number: 2-HEA, as an acrylic monomer), and 0.3 g of 2,2'-azobis(methyl isobutyrate) (manufacturer: KSK, model number: V-601, as a thermal initiator) with 66 ml of butyl acetate and 33 ml of propylene glycol methyl ether acetate. This adhesive composition was subjected to a thermal crosslinking reaction at 80°C for 6 hours to obtain an adhesive. This adhesive has the structure shown in the above chemical formula (7-1). In this case, m is 170, n is 17, and p is 10.

[0047] [Example 3] Adhesive composition and adhesive Example 3 differs from Example 2 in that the acrylic monomer used is butyl acrylate. The adhesive of Example 3 has the structure shown in the above chemical formula (7-2). In this case, in chemical formula (7-2), m is 154, n is 17, and p is 10. Differential scanning calorimetry (DSC, manufacturer: TA Instruments, model: Q500) was performed on the adhesives of Examples 1 to 3. The results are shown in Table 1.

[0048] [Table 1]

[0049] <Evaluation Criteria> The following explanation will use the preparation of adhesive samples and their measurements in Example 1 as an example. The preparation of adhesive samples and measurements in Examples 2 and 3 will be similar. A film-like sample was prepared by applying the adhesive of Example 1 to a thin substrate. The thickness of the adhesive in the sample was 65 μm. This adhesive was irradiated with ultraviolet light at a wavelength of 290 nm as a first light source to induce a photocyclization reaction between the first unsaturated bond sites adjacent to the benzene rings of each of the two modified cinnamic acid monomer structural units in the adhesive, thereby forming a cyclized structure in the cyclized state shown in chemical formula (8) above. Next, this adhesive was irradiated with ultraviolet light at a wavelength of 225 nm as a second light source to induce a photoring-opening reaction in the cyclized structure in the adhesive, resulting in an open ring state shown in chemical formula (9) above. The sample with the adhesive in the open ring state and the sample with the adhesive in the cyclized state were subjected to the following tests, respectively.

[0050] (Peel strength test) In accordance with ASTM D3330, peel strength tests were performed five times each on the adhesives of Examples 1 to 3 using a tensile strength testing machine (manufacturer: ZwickRoell, model: Z0.5TH) in both the open-ring and cyclized states. The results are shown in Table 2.

[0051] [Table 2]

[0052] Referring to Table 2, in five tests, the peel strength of the adhesives in Examples 1-3 in the ring-open state was higher than that of the adhesives in Examples 1-3 in the cyclized state. This demonstrates that the adhesives of the present invention can have different peel strengths by irradiating them with light sources of different wavelengths, and therefore, the adhesives of the present invention can bond or separate two objects from each other.

[0053] (Adhesion test) In accordance with CNS (National Standards of the Republic of China) 11888 (Test Methods for Pressure-Sensitive Adhesive Tapes and Sheets), the adhesives of Examples 1-3 were subjected to adhesion tests five times each in the open and closed states using a Tape Initial Adhesion Rolling Ball Tester (Manufacturer: Gotech Testing Machines Inc., Taiwan; Model: GT-7218-A) and 0.2g or 1.05g metal balls. The results are shown in Tables 3 and 4. The adhesion values ​​in the tables represent the amount of shear (mm), meaning that a lower value indicates higher adhesion.

[0054] [Table 3]

[0055] [Table 4]

[0056] Referring to Tables 3 and 4, in five tests conducted using metal balls of different weights, the tackiness of the adhesives of Examples 1-3 in the ring-open state was higher than that of the adhesives of Examples 1-3 in the cyclized state. This also demonstrates that the adhesives of the present invention can have different tackiness by irradiating them with light sources of different wavelengths, and therefore, the adhesives of the present invention can not only bond two objects together but also separate them again after bonding.

[0057] In summary, the adhesive composition of the present invention, through the interaction between the modified cinnamic acid monomer and the propylene glycol methyl ether acrylate monomer, and further interaction when an acrylic monomer is added to these, can produce an adhesive in which the adhesive strength changes when irradiated with different light sources. Therefore, with the adhesive of the present invention, the adhesive can be repeatedly used to bond or separate two objects from each other, thereby certainly achieving the objective of the present invention.

[0058] In the above, many specific details have been provided to facilitate an overall understanding of the present invention. However, it will be apparent to those skilled in the art that one or more other embodiments can be implemented without providing specific details. Although specific embodiments and variations of the present invention have been described above, the present invention is not limited thereto and encompasses all modifications and equivalent configurations as various configurations included in the spirit and scope of the broadest interpretation.

Claims

1. A modified cinnamic acid monomer, which is an esterified product of the reaction components including cinnamic acid, hydroxyethyl methacrylate, and a catalyst, Propylene glycol methyl ether acrylate monomer, Initiator and A solvent containing butyl acetate, Adhesive composition.

2. The solvent further comprises propylene glycol methyl ether acetate, wherein the amount of butyl acetate in the solvent is greater than the amount of propylene glycol methyl ether acetate. The adhesive composition according to claim 1.

3. If the dose of modified cinnamic acid monomer is 100 parts by weight, the dose of propylene glycol methyl ether acrylate monomer is in the range of 100 to 2000 parts by weight, and the dose of the initiator is in the range of 4 to 6 parts by weight. The adhesive composition according to claim 1.

4. The material further comprises one acrylic monomer selected from the group consisting of 2-hydroxyethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. The adhesive composition according to claim 1.

5. Assuming the total dose of modified cinnamic acid monomer, propylene glycol methyl ether acrylate monomer, acrylic monomer, and initiator is 100 wt%, the dose of modified cinnamic acid monomer is in the range of 4.9 wt% to 9.9 wt%, the total dose of propylene glycol methyl ether acrylate monomer and acrylic monomer is in the range of 90 wt% to 95 wt%, and the dose of initiator is in the range of 0.1 wt% to 0.5 wt%. The adhesive composition according to claim 4.

6. The initiator is at least one selected from the group consisting of thermal initiators and photoinitiators. The adhesive composition according to claim 1.

7. An adhesive comprising a crosslinking reaction product of an adhesive composition according to any one of claims 1 to 6, the product comprising a modified cinnamic acid monomer structural unit represented by the following chemical formula (3) and a propylene glycol methyl ether acrylate monomer structural unit represented by the chemical formula (4). 【Chemistry 1】 【Chemistry 2】

8. When the adhesive is irradiated with a first light source, a photocyclization reaction occurs between the first unsaturated bond sites adjacent to the benzene rings of each of the two modified cinnamic acid monomer structural units in the adhesive, forming a cyclized structure. When irradiated with a second light source, the cyclized structure in the adhesive undergoes a photoring-opening reaction, becoming an open-ring state. The adhesive strength of the adhesive in the cyclized state is less than the adhesive strength of the adhesive in the open-ring state. The adhesive according to claim 7.

9. The first light source has a wavelength in the range of 285 nm to 295 nm. The adhesive according to claim 8.

10. The second light source has a wavelength in the range of 220 nm to 230 nm. The adhesive according to claim 8.

11. The adhesive has a glass transition temperature in the range of -40°C to -60°C. The adhesive according to claim 7.

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