High-barrier two-component solvent-free polyurethane adhesive as well as preparation method and application method thereof

Abstract

The invention discloses a high-barrier two-component solvent-free polyurethane adhesive and preparation and application methods thereof. The high-barrier two-component solvent-free polyurethane adhesive comprises a component A and a component B. The component A comprises, by mass, 30-60% of aromatic polyester polyol and 40-70% of diisocyanate. The component B comprises a mixture of 50 to 70 percent by mass of aromatic polyester polyol, 5 to 20 percent by mass of rosin resin and 20 to 40 percent by mass of polyoxypropylene polyol. The composite film has high bonding strength and is suitable for bonding various aluminized soft package composite structures, the composite film has high barrier property, and the oxygen barrier value is lower than 10 cc / m < 2 >-day.

Description

Technical Field

[0001] This invention belongs to the field of adhesives for flexible packaging, specifically relating to a high-barrier two-component solvent-free polyurethane adhesive and its preparation and application methods. Background Technology

[0002] Flexible packaging materials are gradually replacing rigid packaging materials due to their light weight, convenience, and economy. However, most flexible packaging materials are made of plastic, and their barrier properties, especially oxygen and moisture barrier properties, are significantly reduced compared to traditional rigid packaging materials. Vacuum-depositing a layer of aluminum or alumina on the film surface can greatly improve the barrier properties of flexible packaging materials. However, because the aluminum or alumina layer is very thin, generally around 50-80 nanometers, and relatively brittle, it is prone to forming many invisible defects during transportation and handling, thus affecting the density of the aluminum or alumina layer and consequently its barrier properties. Laminating the aluminized film with adhesives can greatly compensate for the defects on the surface of the aluminized or alumina film, thereby improving its barrier properties. However, different types of adhesives have varying effects on the barrier properties of aluminized structures; not all adhesive-laminated aluminized structures can achieve the required oxygen barrier value. Appropriate raw materials and formulation design are needed to achieve below 10cc / m³. 2 -day oxygen barrier effect. Summary of the Invention

[0003] The purpose of this invention is to provide a two-component solvent-free polyurethane adhesive with excellent barrier properties suitable for aluminized or alumina-plated structures, as well as its preparation and application methods.

[0004] The present invention comprises component A and component B. Component A comprises 30-60% aromatic polyester polyol and 40-70% isocyanate by mass percentage. Component B comprises a mixture of 50-70% aromatic polyester polyol, 5-20% rosin resin and 20-40% polyoxypropylene polyol by mass percentage.

[0005] Further, the diisocyanate is one or more of 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and carbodiimide-modified diphenylmethane diisocyanate.

[0006] Specifically, the aromatic polyester polyol is an aromatic polyester polyol with an index-average molecular weight of 500-2000, which is obtained by polycondensation reaction of phthalic acid or terephthalic acid with ethylene glycol or diethylene glycol. The aromatic polyester polyol is a mixture of one or more different molecular weights.

[0007] Furthermore, the rosin resin is a modified rosin resin with a hydroxyl value of 60-120 mgKOH / g and a softening point of 60-100 degrees Celsius.

[0008] The present invention includes the following steps Preparation of component A: Aromatic polyester polyol and diisocyanate are added to the reaction vessel in sequence, heated to 70-90 degrees Celsius, and reacted for 2-4 hours. When the NCO content reaches the theoretical value, the reaction ends and component A is obtained.

[0009] Preparation of component B: Aromatic polyester polyol, polyoxypropylene polyol and rosin resin are added to the reaction vessel in sequence, heated to 80-110 degrees and stirred for 2-4 hours. When the hydroxyl value reaches the theoretical value, component B is obtained.

[0010] The two-component solvent-free polyurethane adhesive of the present invention, prepared by selecting aromatic polyester polyols and modified rosin resin, not only has excellent bonding performance, but also achieves an oxygen barrier value of less than 10 cc / m after being composited with BOPP / MCPP. 2 -day oxygen barrier level. Detailed Implementation

[0011] Example 1: 380 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 175 mg KOH / g) and 620 g of MDI-50 were added to a reactor and reacted at 75 degrees Celsius for 2 hours to obtain component A. 580 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 175 mg KOH / g), 150 g of rosin resin (hydroxyl value of 110 mg KOH / g, softening point of 90 degrees Celsius), and 270 g of polyoxypropylene triol (molecular weight 450) were added to a reactor and stirred at 100 degrees Celsius for 1 hour to obtain component B. The ratio of component A to component B was 100:70.

[0012] Example 2: 400 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 115 mg KOH / g) and 600 g of MDI-50 were added to a reactor and reacted at 75°C for 2 hours to obtain component A. 520 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 175 mg KOH / g), 100 g of rosin resin (hydroxyl value of 110 mg KOH / g, softening point of 90°C), and 380 g of polyoxypropylene triol (molecular weight 450) were added to a reactor and stirred at 100°C for 1 hour to obtain component B. The ratio of component A to component B was 100:65.

[0013] Example 3: 350 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 191 mg KOH / g) and 650 g of MDI-50 were added to a reactor and reacted at 75°C for 2 hours to obtain component A. 520 g of aromatic polyester polyol (obtained by condensation polymerization of phthalic acid and diethylene glycol, with a hydroxyl value of 191 mg KOH / g), 100 g of modified rosin resin (hydroxyl value of 70 mg KOH / g, softening point of 95°C), and 380 g of polyoxypropylene triol (molecular weight 450) were added to a reactor and stirred at 100°C for 1 hour to obtain component B. The ratio of component A to component B was 100:65.

[0014] Comparative Example 1: 180 g of polypropylene glycol (molecular weight 1000), 240 g of refined castor oil polyol (hydroxyl value 165 mg KOH / g), and 580 g of MDI-50 were added to a reactor and reacted at 80 degrees Celsius for 2 hours to obtain component A. 330 g of polypropylene triol (molecular weight 450) and 670 g of refined castor oil polyol (hydroxyl value 165 mg KOH / g) were stirred in a reactor at 50 degrees Celsius for 1 hour to obtain component B. The ratio of component A to component B was 100:60.

[0015] Comparative Example 2: 400 g of aliphatic polyester polyol (obtained by condensation polymerization of adipic acid and diethylene glycol, with a hydroxyl value of 115 mg KOH / g) and 600 g of MDI-50 were added to a reactor and reacted at 75 degrees Celsius for 2 hours to obtain component A. 640 g of aliphatic polyester polyol (obtained by condensation polymerization of adipic acid and diethylene glycol, with a hydroxyl value of 145 mg KOH / g) and 360 g of polyoxypropylene triol (molecular weight 450) were added to a reactor and stirred at 50 degrees Celsius for 1 hour to obtain component B. The ratio of component A to component B was 100:70.

[0016] The adhesives from the examples and comparative examples were mixed in a specific ratio and then laminated into a BOPP / MCPP structure. The adhesive application rate was controlled at 1.6-1.9 grams per square meter. The film rolls were then placed in a 40-degree oven for 24 hours for curing. Afterward, peel strength and oxygen barrier value were tested. The oxygen barrier value test was conducted on a MOCON OX-TRAN device at a temperature of 23 degrees Celsius and 0% humidity, with a test area of ​​50 cm². 2 .

[0017] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Peel strength (N / 15mm) 1.2 1.1 1.0 1.2 1.3 <![CDATA[Oxygen barrier value (cc / m 2 -day, 23˚C, 0% humidity)]]> 6.8 7.6 9.2 21 13.6 In summary, the high-barrier two-component solvent-free polyurethane adhesive prepared in the embodiments of the present invention not only has good peel strength, but also an oxygen barrier value of less than 10 cc / m 2 -day, significantly lower than the adhesive of the comparative example (prepared without aromatic polyester polyols and rosin resin, but using aliphatic polyester polyols or castor oil).

Claims

1. A high-barrier two-component solvent-free polyurethane adhesive, characterized in that: It includes component A and component B. Component A comprises 30-60% aromatic polyester polyol and 40-70% diisocyanate by mass percentage. Component B comprises a mixture of 50-70% aromatic polyester polyol, 5-20% rosin resin and 20-40% polyoxypropylene polyol by mass percentage.

2. The high-barrier two-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The diisocyanate is one or more of 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and carbodiimide-modified diphenylmethane diisocyanate.

3. The high-barrier two-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The aromatic polyester polyol is an aromatic polyester polyol with an index-average molecular weight of 500-2000. The aromatic polyester polyol is obtained by polycondensation of phthalic acid or terephthalic acid with ethylene glycol or diethylene glycol. The aromatic polyester polyol is a mixture of one or more aromatic polyester polyols with different molecular weights.

4. The high-barrier two-component solvent-free polyurethane adhesive according to claim 1, characterized in that: The rosin resin is a modified rosin resin, and is obtained by mixing one or more modified rosin resins in any proportion, with a hydroxyl value of 60-120 mgKOH / g and a softening point of 60-100 degrees.

5. A method for preparing a high-barrier two-component solvent-free polyurethane adhesive as described in any one of claims 1-4, characterized in that: Add 30-60% aromatic polyester polyol and 40-70% diisocyanate to a reaction vessel, gradually raise the temperature to 70-90 degrees Celsius, and react for 2-4 hours to obtain component A; add 50-70% aromatic polyester polyol, 5-20% rosin resin and 20-40% polyoxypropylene polyol to a reaction vessel, and stir at 90-110 degrees Celsius for 2-4 hours to obtain component B.

6. A method for applying the high-barrier two-component solvent-free polyurethane adhesive as described in any one of claims 1-4, characterized in that: Components A and B of the adhesive were mixed at a weight ratio of 100:50-100:

90. The resulting adhesive was applied to a composite BOPP / MCPP structure and cured at 40 degrees Celsius for 24 hours. The resulting composite film had an oxygen barrier value of less than 10 cc / m³. 2 -day.