When a free radical is excited from the hydroxyl monomer, the hydroxyl monomer can provide a bridging point which can connect with the methacrylic monomer or the acrylic monomer. The hydroxyl monomer can be 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or a combination thereof. However, the present disclosure is not limited thereto.

The crosslinker of the adhesive composition can have multi-functional groups so as to facilitate the cross-linking reaction. Specifically, the crosslinker can be an isocyanate compound having at least three isocyanate groups (—NCO). For example, the crosslinker can be hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), olylene diisocyanate (TDI), or xylene diisocyanate (XDI).

The catalyst of the adhesive composition can be a metal chelate compound containing iron, titanium, or aluminum, such as ferric acetylacetonate, tris(2,4-hexanedione) titanium, tris(2,4-hexanedione)aluminum, or a combination thereof.

The solvent of the adhesive composition can be toluene (boiling point: 110.6° C.), propylene glycol methyl ether acetate (boiling point: 149° C.), ethyl acetate (boiling point: 77.1° C.), or other high boiling point solvents. For example, the boiling point of the solvent can range from 70° C. to 160° C.

In order to prove that the adhesive composition of the present disclosure can be used to form the protective membrane, a copolymer in Preparation Examples 1 to 4 can be polymerized according to the method below. The copolymer in Preparation Examples 1 to 4 is used to prepare the adhesive composition, so as to manufacture the protective membrane in Examples 1 and 2 and Comparative Examples 1 and 2.

Preparation Examples 1 to 4

According to the contents listed in Table 1, monomers to form the B block segment (the methacrylic monomer, the acrylic monomer, and the hydroxyl monomer), a solvent (ethyl acetate), and an initiator (azobisisobutyronitrile) are added into a glass reactor (to form a first reactant mixture). The first reactant mixture is stirred by a rate of 300 rpm and heated to a temperature ranging from 65° C. to 70° C. in an atmosphere of flowing nitrogen, so as to perform a first state reaction at a constant temperature. After 8 hours of reaction (a conversion rate being 95%), an intermediate product is obtained. A solid content of the intermediate product is 40 wt %, and a viscosity of the intermediate product ranges from 1500 cps to 2000 cps.

According to the contents listed in Table 2, monomers to form the A block segment (the methacrylic monomer, the acrylic monomer, and the hydroxyl monomer), a solvent (ethyl acetate), and an initiator (azobisisobutyronitrile) are added into the glass reactor and mixed with the intermediate product (to form a second reactant mixture). The second reactant mixture is stirred by a rate of 300 rpm and at a temperature ranging from 65° C. to 70° C., so as to perform a second state reaction in an atmosphere of flowing nitrogen. After 8 hours of reaction, a polymerizing product is obtained. A solid content of the polymerizing product is 35 wt %, and a viscosity of the intermediate product ranges from 2000 cps to 2500 cps. The solvent is removed, and then an acrylic copolymer (an acrylic block copolymer in Preparation Examples 2 and 3) is obtained.

The difference between the acrylic copolymers in Preparation Examples 1 to 4 is that the amounts of the A block segment and the B block segment are different. Specifically, the acrylic copolymer in Preparation Example 1 is completely polymerized from the monomers to form the A block segment, and the acrylic copolymer in Preparation Example 4 is completely polymerized from the monomers to form the B block segment. The acrylic block copolymer in Preparation Examples 2 and 3 includes the A block segment and the B block segment, while having different amounts. Specific amounts are listed in Table 3.

The amounts of the A block segment and the B block segment, the molecular weight of the acrylic copolymer, and the glass transition temperatures of the A block segment and the B block segment are listed in Table 3. The glass transition temperatures of the A block segment and the B block segment are measured by a dynamic mechanical analyzer.

TABLE 1

Preparation
Preparation
Preparation
Preparation

Monomers to form B block segment (phr)
Example 1
Example 2
Example 3
Example 4

Methacrylic
Methyl methacrylate
—
29
29
29

monomer

Acrylic
Methyl acrylate
—
5
5
5

monomer
n-Butyl acrylate
—
8
8
8

2-Ethylhexyl acrylate
—
50
50
50

Hydroxyl
2-Hydroxyethyl acrylate
—
8
8
8

monomer

Initiator
Azobisisobutyronitrile
—
0.1
0.1
0.1

Solvent
Ethyl acetate

150
150
150

Polymerization temperature
70° C.