KR20130039512A

KR20130039512A - Method for preparing the adhesive with low surface energy

Info

Publication number: KR20130039512A
Application number: KR1020110104121A
Authority: KR
Inventors: 김현중; 박지원; 배경열
Original assignee: 서울대학교산학협력단
Priority date: 2011-10-12
Filing date: 2011-10-12
Publication date: 2013-04-22

Abstract

PURPOSE: An adhesive is provided to have low surface energy by having a lot of fluorine on the surface of the adhesive, thereby improving wettability and improving adhesion to various substrates. CONSTITUTION: A manufacturing method of an adhesive comprises a step of mixing a photoinitiator into 2-ethylhexyl acrylate, acrylic acid, and 2,2,2-trifluoromethyl methacrylate, and photopolymerizing the mixture. The photoinitiator is hydroxy dimethyl acetophenone. The comprised amount of the 2,2,2-trifluoromethyl methacrylate is 1-30 weight%. The adhesive is manufactured by the method and has a structure represented by chemical formula 1. In chemical formula 1, each of x, y, and z is an integer from 1-10.

Description

Method for preparing the adhesive with low surface energy {Method for Preparing the Adhesive with Low Surface Energy}

The present invention relates to a method for producing a pressure-sensitive adhesive having a low surface energy, and more particularly, to a method for producing a pressure-sensitive adhesive by photopolymerizing 2-ethylhexyl acrylate, acrylic acid and a photopolymerizable fluorine-based compound.

A pressure sensitive adhesive refers to a nonmetallic material that is adhered to a surface of various materials using low pressure. In particular, acrylic pressure-sensitive adhesives are used in various industrial fields because they have advantages such as deterioration characteristics, transparency and thermal stability, for example, they are used in the medical field, aircraft, spacecraft, electronic devices, cold and automotive industries.

However, acrylic adhesives have low adhesion to plastic substrates, for example, plastic substrates having low surface energy, such as polyethylene (PE), polypropylene (PP), or polytetrafluoroethylene (PTFE). There is a problem falling. This is because the surface energy of the plastic substrate is low, and the adhesive is hardly wet with the plastic substrate. In order to solve this problem, a method of increasing the adhesive force by increasing the surface energy of the substrate by pretreatment on the surface of the plastic substrate in general has been studied. The surface pretreatment method may be corona, plasma treatment, or primer treatment. However, this pretreatment method has a problem in that the cost and damage to the surface of the plastic substrate. Therefore, the present inventors devised a method for improving the wettability of the pressure-sensitive adhesive to solve the above problems and completed the present invention.

An object of the present invention is to provide a pressure-sensitive adhesive having a low surface energy and a method of manufacturing the same.

According to a preferred embodiment of the present invention, the preparation of a pressure-sensitive adhesive having low surface energy is characterized by mixing and photopolymerizing a photoinitiator into 2-ethylhexyl acrylate, acrylic acid and 2,2,2-trifluoroethyl methacrylate. Provide a method.

According to another suitable embodiment of the present invention, the photoinitiator is hydroxydimethylacetophenone.

According to another suitable embodiment of the present invention, 2,2,2-trifluoroethyl methacrylate is characterized in that 1 to 30% by weight relative to the total weight of the adhesive.

According to another suitable embodiment of the present invention, there is provided a pressure-sensitive adhesive having a structure of formula (1).

[Formula 1]

Wherein x, y and z are integers from 1 to 10.

The pressure-sensitive adhesive prepared in the present invention has a low surface energy because a large amount of fluorine is distributed on the surface of the pressure-sensitive adhesive, and as a result, the wettability is improved to have high adhesion to various substrates.

Figure 1 shows the photopolymerization behavior according to the content of the fluorine-based compound of the pressure-sensitive adhesive prepared in the present invention.
Figure 2 shows the infrared spectroscopy (FTIR) peaks of TFMA monomer (a), Example 3 (b), Comparative Example 1 (c).
Figure 3 shows by measuring the contact angle and surface energy of the pressure-sensitive adhesive prepared in the present invention.
Figure 4 shows the initial tack (probe tack) of the pressure-sensitive adhesive prepared in the present invention.
Figure 5 shows the peel strength (Peel strength) when the pressure-sensitive adhesive prepared in the present invention is applied to various substrates.

In the present invention, the pressure-sensitive adhesive is characterized in that it comprises a first component consisting of a monomer of a soft part, a second component consisting of a monomer of a hard part, and a fluorinated compound.

The hard part of the adhesive shows the adhesive property and mainly acrylic acid (Tg: 106 ℃) is used. Moreover, since acrylic acid has a carboxyl group, the cohesion force of an adhesive can be improved through bridge | crosslinking.

The light monomer has a low glass transition temperature (Tg) and is an important part that plays a role in controlling the tack of the adhesive. Usually acrylates or methacrylates having 4 to 17 carbons are used, and examples thereof include butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate or decyl acrylate. 2-ethylhexyl acrylate is used more preferably.

In addition, a plasticizer, a polymerization inhibitor, and a filler may be added as an additive, and as the plasticizer, polybutene may be preferably used. The plasticizer is preferably used 5 to 15% by weight based on the weight of the adhesive.

In the present invention, a fluorine-substituted monomer is used as a material having a low surface energy. Fluorine-substituted compounds are characterized by low surface energy and resistance to chemicals. In the present invention, as the monomer substituted with fluorine, 2,2,2-trifluoroethyl methacrylate and polytetrafluoroethene can be preferably used. The pressure-sensitive adhesive of the present invention preferably contains 1 to 30% by weight, more preferably 5 to 20% by weight of the total weight of the fluorine-based compound. If it is less than 1% by weight, a small amount of fluorine groups are included, so the effect of lowering the surface energy is insignificant. If it exceeds 30% by weight, the adhesive force (Tack) decreases and the adhesion decreases.

As a preferred embodiment of the present invention, a photoinitiator is mixed with photoinitiator to 2-ethylhexyl acrylate as the first component, acrylic acid as the second component, and 2,2,2-trifluoroethyl methacrylate as the fluorine monomer. The adhesive which has a fluorine group is manufactured.

Photopolymerization using UV is used in many fields, and is used not only for curing the ink but also for coating adhesion. Photopolymerization using UV has the advantages of high polymerization rate, low energy consumption, polymerization at room temperature, and small polymerization equipment area. Photopolymerization does not have a specific condition, unlike a solution polymerization method that starts using heat, and a known method may be used.

Preferred pressure-sensitive adhesives synthesized in the present invention include compounds represented by the following general formula (1).

[Formula 1]

Wherein x, y and z are integers from 1 to 10.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited by Examples.

Example 1

The acrylic pressure-sensitive adhesive was polymerized in the composition ratio of Table 1 below. First, 90 wt% (180 g) of 2-ethylhexyl acrylate, 5 wt% (10 g) of acrylic acid, and 5 wt% (10 g) of 2,2,2-trifluoroethyl methacrylate are put into a 500 mL round flask and stirred. . Next, hydroxydimethylacetophenone, a photoinitiator, was mixed with 0.2 wt% (0.4 g) of the total monomer weight, and a 250W lamp (SP-0-250UB, USHIO Inc., System Company, Japan) was mixed at three minute intervals. Irradiation was performed 5-10 times until the double bond peak disappeared and photopolymerization reaction was carried out. Nitrogen gas was added to prevent the polymerization inhibitory effect by oxygen during photopolymerization. Nitrogen was pre-injected 30 minutes before the reaction and nitrogen was continuously added during the reaction. While performing the reaction at 20 to 100 ° C., 200 g of ethyl acetate, 20 g of polybutane as a plasticizer and 2 g of hydroxydimethylacetophenone as a photoinitiator were further added to synthesize an adhesive.

The synthesized pressure-sensitive adhesive was coated with polyethylene terephthalate (PET, SK Chemical, Korea) film with corona treatment to a thickness of 100 μm, and then conveyor belt type 100W high pressure mercury lamp, main wavelength: 365 nm). After drying for 30 minutes in an 80 ^° C oven and stored at 22 ^° C ± 2 and 60 ± 5% RH for 24 hours.

Example 2

The same method as in Example 1, except that 85 wt% (170 g) of 2-ethylhexyl acrylate, 5 wt% (10 g) of acrylic acid, and 10 wt% (20 g) of 2,2,2-trifluoroethyl methacrylate were used. An adhesive was synthesize | combined by the.

Example 3

The same method as in Example 1, except that 80 wt% (160 g) of 2-ethylhexyl acrylate, 5 wt% (10 g) of acrylic acid, and 15 wt% (30 g) of 2,2,2-trifluoroethyl methacrylate were used. An adhesive was synthesize | combined by the.

Comparative Example 1

The pressure-sensitive adhesive was synthesized in the same manner as in Example 1 except that 95% by weight (190 g) of 2-ethylhexyl acrylate and 5% by weight (10 g) of acrylic acid were used.

Ingredient (% by weight) Example 1 Example 2 Example 3 Comparative Example 1 2-HEA 90 85 80 95 AA 5 5 5 5 TFMA 5 10 15 0 HP-8 0.2 0.2 0.2 0.2

Physical properties of the pressure-sensitive adhesive prepared in the present invention was measured by the following method.

Contact angle

The sample was coated with a thickness of 90 μm on a glass plate, and then cured with a light quantity of 600 mJ / cm ² . The contact angle was measured using a goniometer, SEO 300A contact angle measuring device, Surface & Electro-Optics Co., Republic of Korea, and measured using water, diodomethane, and ethylene glycol. Surface energy was calculated using the / base method.

X-ray photoelectron spectroscopy (X- ray photoelectron spectroscopy , XPS )

X-ray photoelectron spectroscopy (XPS) was performed by UHV multipurpose surface analysis system (SIGMA PROBE, Thermo, UK) for F element analysis of the adhesive surface under vacuum of <10 ^-10 mbar. A 100 K (15 KV and 6.7 MW) Al K (1486.6 eV) anode was used, and the pass energy in constant analyser energy (CAE) mode was 30 eV.

Adhesive property

Initial tack was measured using a 5 mm stainless steel cylindrical probe using a physical property analyzer (Texture Analyzer, TA-XT2i, Micro Stable Systems, UK). The initial adhesive force measures the force of the adhesive debonding with the probe as the probe approaches the surface of the adhesive and is separated after a certain time of contact.

Peel strength is obtained by attaching a sample to various plastic materials (Teflon, phenolic resin, PP, PVC, ABS) and stainless steel substrate (SUS substrate), and then passing the 2 kg rubber roller twice, Measure after standing for 24 minutes. The peel rate is 300 mm / min at room temperature, and the peel data is measured by the average force during the peel period.

Figure 1 shows the photopolymerization behavior according to the content of the fluorine-based compound of the pressure-sensitive adhesive prepared in the present invention (4.0mW / cm ² ). In FIG. 1, as a result of examining the 810 cm ^-1 C = C peak, when the content of TFMA is 0% (Comparative Example 1), the peak decreases most rapidly, and as the content of TFMA increases, the time for decreasing the peak decreases. Could know. This was due to the shielding effect of methacrylate of TFMA and the stability of the fluorine group.

Figure 2 shows the FTIR peaks of TFMA monomer (a), Example 3 (b), and Comparative Example 1 (c). Since the pressure sensitive adhesive of Comparative Example 1 is a copolymer of 2-ethylhexyl acrylate and acrylic acid, and the pressure sensitive adhesive of Example 2 has a fluorine element in addition to 2-ethylhexyl acrylate and acrylic acid, most of the peaks Similar. In addition, since it has a fluorine element, it can be seen that the same CF peak (1200 to 1300 cm ^-1 ) as the peak in the 1100 to 1300 cm ^-1 region of TFMA is observed. Therefore, in Example 3, it can be seen that fluorine was well applied to the acrylic adhesive by photopolymerization.

Figure 3 shows by measuring the contact angle and surface energy of the pressure-sensitive adhesive prepared in the present invention. Since the TFMA monomer has a low surface tension of 19 mN / m, it can be seen that the contact angle of water increases as the content of TFMA increases in the pressure-sensitive adhesive. In addition, as a result of calculating the surface energy using the acid / base method, it can be seen that the surface energy is lowered to 37 mN / m when the TFMA content is 20% by weight.

Table 2 below shows the yield of fluorine element on the surface of the pressure-sensitive adhesive prepared in the present invention. As can be seen from Table 2, it can be seen that as the content of TFMA increases, the fluorine element appears well on the pressure-sensitive adhesive surface.

Example 1 Example 2 Example 3 Comparative Example 1 F element ratio (%) 2.46 5.08 9.72 0

Figure 4 shows the initial tack (probe tack) of the pressure-sensitive adhesive prepared in the present invention. Referring to FIG. 4, as the content of TFMA was increased to 10 wt%, the initial adhesive strength increased from 150 to 300 g, and the value of 300 g was similar to 10 wt% for 20 wt%. This is because the surface energy of the pressure-sensitive adhesive is lowered by TFMA to improve the wettability.

Figure 5 shows the peel strength (Peel strength) when the pressure-sensitive adhesive prepared in the present invention is applied to various substrates. 5a shows polypropylene (PP), FIG. 5b shows polyvinyl chloride (PVC), FIG. 5c shows ABS (acrylonitrile butadiene styrene), and FIG. 5d shows peeling after 30 minutes and 24 hours after attaching the adhesive to a stainless steel (SUS) substrate. The strength is measured. When the pressure sensitive adhesive was applied to PP, ABS, PVC, and SUS substrates, the peel strength increased with increasing TFMA content. This is because the wettability is improved as the surface energy of the adhesive is lowered, thereby increasing the adhesive strength. In the case of FIG. 5A it was increased in 10 wt% TFMA from 300 g / 25 mm to 1000 g / 25 mm. In the case of using the PVC substrate of Figure 5b, even when using the ABS substrate in Figure 5c the peel strength was increased as the content of TFMA increased. In addition, even when using the stainless steel substrate of Figure 5d was measured the strength of 1500 g / 25 mm in proportion to the adhesion time and the content of TFMA. (Surface energy of substrate PP: 33 mN / m, ABS: 42 mN / m, PVC: 39 mN / m, SUS: 200 ~ 1000 mN / m)

Claims

A method for producing a pressure-sensitive adhesive having low surface energy, characterized by mixing a photoinitiator with 2-ethylhexyl acrylate, acrylic acid, and 2,2,2-trifluoroethyl methacrylate and photopolymerizing it.

The method according to claim 1,
The photoinitiator is a manufacturing method of the pressure-sensitive adhesive, characterized in that hydroxydimethylacetophenone.

The method according to claim 1,
The 2,2,2-trifluoroethyl methacrylate is a pressure-sensitive adhesive production method, characterized in that 1 to 30% by weight relative to the total weight of the pressure-sensitive adhesive.

Pressure-sensitive adhesive prepared by the method of claim 1, having a structure of formula (1).
[Formula 1]

Wherein x, y and z are integers from 1 to 10.