CN1244662C - Dry type compound polyurethane adhesive and its preparation method - Google Patents

Abstract

The invention discloses a dry composite polyurethane adhesive and a manufacturing method thereof. It is a two-component adhesive, characterized in that its components and parts by weight are: 10 parts of the main agent, 0.5 to 10 parts of the curing agent, the main agent is polyester polyol dissolved in an organic solvent, the curing agent It is an organic solvent solution containing polyisocyanate prepolymer, and the polyisocyanate prepolymer is a product obtained by reacting isocyanate and trimethylolpropane. After the main agent of the polyurethane dry composite adhesive of the present invention is mixed with a curing agent, it can be directly applied to a gravure gluing dry composite machine. The compounded product has high initial bond strength, and can be used in downstream slitting and bag-making processes after aging for more than 24 hours in an environment of 50±5°C.

Description

A kind of dry compound polyurethane adhesive and its manufacturing method

technical field

The invention relates to a polyurethane dry composite adhesive. Specifically relates to a dry composite polyurethane adhesive that can effectively improve the bonding strength to biaxially stretched polypropylene film (BOPP).

Background technique

In recent years, composite films containing two or more layers of different films with more comprehensive physical and chemical properties have been widely used in the packaging of food and other daily necessities. The types of films used in the composite process mainly include polyethylene, polypropylene, nylon, polyester, polyvinyl chloride and aluminum foil. Among them, BOPP film is known as the "Packaging Queen" due to its good gloss, easy printing, and low price, and it is widely used.

Polyurethane adhesives are usually used in industry to bond various plastic films or metal foils. Among the processes used, the most popular is dry compounding, that is, the adhesive is evenly coated on a layer of film according to a certain amount of glue, and the dispersion carrier (solvent or water) of the adhesive is dried through the drying channel of the coating machine. It is then glued together with another film.

As we all know, polyurethane is a highly polar polymer, while polyethylene and polypropylene in plastic films are typical non-polar polymers, and the compatibility between the two is poor. According to the basic theory of adhesion, "compatibility", "similar polarity", and "similar surface tension" are often necessary conditions for good adhesion. For this reason, in the industry, the surface of non-polar polyethylene and polypropylene films is treated with "corona", so that polar groups are introduced into the surface to be bonded, and the surface tension is increased to above 38 or even 40 dynes. Nevertheless, quality incidents of weak bonds still occur frequently, especially when BOPP films are included in the composite structure. There are two main reasons for this: on the one hand, after the film is "corona" treated, the surface tension of its "corona" treated surface will continue to decrease over time; on the other hand, BOPP films often need to be printed before compounding. , During the printing process, the "corona" treated surface will be subject to various pollutions, which will weaken the effect of its surface treatment. In consideration of this reason, a polyurethane dry composite adhesive disclosed by the present invention introduces non-polar functional groups into the molecular structure of polyurethane, which improves its "affinity" with non-polar polymers, so that the adhesive can stick to BOPP. The bonding strength is greatly improved, which can effectively avoid related quality accidents in the compounding process.

Previous work has involved polyurethane adhesives for dry lamination. USP 4206299, EP349839, etc. disclose the technology of 135 ℃ high temperature cooking polyurethane composite adhesive; CN1232851A, CN 1355268A, etc. disclose the technology of 120 ℃ high temperature cooking polyurethane composite adhesive. Polyurethane composite adhesive technology. These patents do not involve the technology of improving the "affinity" between polyurethane and polyolefin films by introducing non-polar alkyl chains into the molecular structure of polyurethane.

Contents of the invention

The technical problem to be solved in the present invention is to disclose a dry composite polyurethane adhesive and its manufacturing method, so as to overcome the above-mentioned defects in the prior art.

The dry composite polyurethane adhesive of the present invention is a two-component adhesive, and its components and parts by weight are:

Main agent 10 parts

Curing agent 0.5~10 parts

The main agent is an organic solvent containing polyester polyol, and the weight concentration of polyester polyol is 50-80%;

The said polyester polyol contains a branched chain structure, a functionality of 2-3, a relative molecular mass of 3,000-10,000, an acid value of <3mgKOH/g, a glass transition temperature of <-20°C, and a softening point of 20-80°C, which are particularly prominent It is characterized in that it has a structure with 1 to 8% by mass of terminal long-chain alkyl groups.

The curing agent is an organic solvent containing a polyisocyanate prepolymer, and the weight concentration of the isocyanate prepolymer is 50-75%;

Polyisocyanate prepolymer is the reaction product of isocyanate and trimethylolpropane according to the following molar ratio: [-NCO]:[-OH]=3:1; its function is to make the terminal isocyanate group (-NCO) It reacts with the terminal hydroxyl group (-OH) of the main agent, and forms a cross-linked polyurethane structure by utilizing the multifunctional characteristics of the polyisocyanate prepolymer, so that the composite film has certain heat resistance, chemical resistance and further improves the adhesiveness of the adhesive. body strength.

Said organic solvent is selected from one of ethyl acetate, toluene or butanone or a mixture thereof.

The preparation method of dry composite polyurethane adhesive of the present invention comprises the steps:

(1) Preparation of polyester polyol: a classic bulk stepwise polymerization reaction;

Two or more dibasic acids (such as adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, phthalic anhydride, etc.), one or more Diols (such as ethylene glycol, 1,4-butanediol, neopentyl glycol, 2-methylpropanediol, diethylene glycol, etc.), one or more than one trifunctional acid or alcohol (such as glycerol , trimethylolpropane, trimellitic anhydride, etc.), one or more than one long alkyl chain monofunctional acid or alcohol (such as lauric acid, stearic acid, isooctyl alcohol, etc.) in the presence of a catalyst, vacuum melt polycondensation, The reaction temperature is 160-250°C, the reaction time is 20-30 hours, the ratio of the total equivalent of alcohol to acid is 1.05-1.5: 1, to ensure that the synthesized polyester polyol has the characteristics of hydroxyl-terminated structure,

The catalyst used is selected from tetrabutyl titanate, tetraisopropanol titanate, antimony trioxide, antimony acetate, stannous chloride or dibutyltin dilaurate, etc.;

The synthesized polyester polyol has a branched chain structure, a functionality of 2-3, a relative molecular mass of 3,000-10,000, an acid value of <3mgKOH/g, a glass transition temperature of <-20°C, and a softening point of 20-80°C. The outstanding feature is that it has a structure of 1-8 mass % terminal long-chain alkyl groups.

(2) Preparation of curing agent: react isocyanate and trimethylolpropane at 50-90°C for 5-10 hours, the molar ratio of isocyanate to trimethylolpropane is: -NCO:-OH=3: 1;

Its function is to react the terminal isocyanate group (-NCO) with the terminal hydroxyl group (-OH) of the main agent, and use the multifunctional characteristics of the polyisocyanate prepolymer to form a cross-linked polyurethane structure, so that the composite film has a certain Heat resistance, chemical resistance and further increase the bulk strength of the adhesive.

When the polyurethane dry composite adhesive disclosed by the invention is applied in a dry composite process, the main agent and the curing agent are mixed in a certain ratio to form a high-solid-content low-viscosity polyurethane adhesive soluble in an organic solvent. The mixing ratio is determined by the hydroxyl value of the main agent and the isocyanate value of the curing agent. Usually an excess of isocyanate is required to ensure that after the water in the solvent consumes a part of the isocyanate group, there are still enough isocyanate groups in the system to react with hydroxyl groups, so as not to cause incomplete curing of the adhesive. A more ideal situation is that the isocyanate group can be further excessive, so that in addition to the consumption of the above two parts, there is still a certain amount of isocyanate group that reacts with the trace moisture adsorbed on the surface of the composite film and the active hydrogen atoms contained on the surface, thereby further Improve composite bond strength. Therefore, the ratio [NCO]/[OH]=1-10 of the amount of curing agent isocyanate substance and the amount of main agent hydroxyl substance of the polyurethane dry composite adhesive involved in the present invention is more ideally [NCO]/[OH ]=1.5-2.5.

After the main agent of the polyurethane dry composite adhesive involved in the present invention is mixed with a curing agent, its viscosity is adjusted to be lower than 1000 cps at room temperature through the dilution of an organic solvent, and then it can be directly applied to a gravure gluing dry composite machine. The compounded product has high initial bond strength, and can be used in downstream slitting and bag-making processes after aging for more than 24 hours in an environment of 50±5°C.

Detailed ways

Example 1

Put 0.8 mol of ethylene glycol and 0.6 mol of neopentyl glycol into the three-neck flask reactor, raise the temperature to 100°C, add 0.02 g of the catalyst stannous chloride, and then continue to add 0.5 mol of isophthalic acid and 0.5 mol of adipic acid, The polyester polyol was prepared by melt vacuum polycondensation method, its hydroxyl value was 21.0 mgKOH/g, and its acid value was 0.8 mgKOH/g. The above-mentioned polyester polyol is dissolved in ethyl acetate with a solid content of 75% to obtain the main agent of the polyurethane dry composite adhesive. (main agent 1)

Put 3mol of toluene diisocyanate (TDI) and 220 grams of ethyl acetate into a three-neck flask reactor, control the temperature of the reactant between 60-90°C, add 1mol of molten trimethylolpropane (TMP) dropwise, add dropwise Continue to react for 3-6 hours after completion to obtain a curing agent for polyurethane dry composite adhesive with a solid content of 75%. (curing agent 1)

Example 2: 0.7mol ethylene glycol, 0.7mol neopentyl glycol, and 0.12mol trimethylolpropane are dropped into a three-necked flask reactor, the temperature is raised to 100° C., catalyzer tin protochloride 0.03 g is added, and then the 0.45 mol of phthalic acid, 0.55 mol of adipic acid, and 0.1 mol of lauric acid were used to prepare polyester polyol by melting vacuum polycondensation method, the hydroxyl value was 22.3 mgKOH/g, and the acid value was 0.6 mgKOH/g. The above-mentioned polyester polyol is dissolved in ethyl acetate with a solid content of 75% to obtain the main agent of the polyurethane dry composite adhesive. (main ingredient 2)

Example 3: 0.5mol diethylene glycol, 0.9mol ethylene glycol, and 0.06mol pentaerythritol are dropped into a three-necked flask reactor, the temperature is raised to 100° C., 0.03 g of catalyst tin protochloride is added, and then 0.5 mol of isophthalic acid is added. mol, 0.5mol of sebacic acid, and 0.1mol of stearic acid, the polyester polyol was prepared by melting vacuum polycondensation method, its hydroxyl value was 22.8mgKOH/g, and its acid value was 0.5mgKOH/g. The above-mentioned polyester polyol is dissolved in ethyl acetate with a solid content of 75% to obtain the main agent of the polyurethane dry composite adhesive. (main agent 3)

Example 4: Put 0.5mol of ethylene glycol, 0.9mol of 2-methylpropanediol, and 0.1mol of isooctyl alcohol into a three-neck flask reactor, raise the temperature to 100°C, add 0.03g of catalyst stannous chloride, and then continue to add terephthalate 0.25 mol of formic acid, 0.2 mol of phthalic anhydride, and 0.1 mol of trimellitic anhydride were used to prepare polyester polyol by melting vacuum polycondensation method. The hydroxyl value was 21.9 mgKOH/g, and the acid value was 0.9 mgKOH/g. The above-mentioned polyester polyol is dissolved in ethyl acetate with a solid content of 75% to obtain the main agent of the polyurethane dry composite adhesive. (main ingredient 4)

Mix the main ingredients of the above examples with the curing agent of Example 1 at a mass ratio of 5:1 to obtain the corresponding polyurethane dry composite adhesive, which are respectively applied to CPP (25μ)/BOPET (12μ) and CPP (25μ)/ Table 1 lists the bond strength results of the dry composite process of the two structures of BOPP (28μ) after curing at 50°C for 48 hours. After the long-chain alkane group is introduced into the molecular structure of the polyurethane dry composite adhesive, its adhesion effect to BOPP is greatly improved, while the adhesion effect to PET is not significantly affected.

Table 1 Characteristics and composite peel strength of various polyurethane dry composite adhesives serial number feature CPP/BOPET(N/15mm) CPP/BOPP(N/15mm) Main agent 1 Main agent 2 Main agent 3 Main agent 4 No introduction of long-chain alkane group Introduction of long-chain alkane group Introduction of long-chain alkane group Introduction of long-chain alkane group 10.789.8510.2610.92 0.821.561.821.68

Claims (8)

1. a dry type compound polyurethane adhesive for a kind of two component adhesive, is characterized in that, its component and parts by weight are:

10 parts of hosts

0.5～10 part in solidifying agent

Said host is the organic solvent that contains polyester polyol;

Said polyester polyol contains branched structure, and functionality 2-3, relative molecular mass are 3,000-10, and 000, acid number＜3mgKOH/g, second-order transition temperature＜-20 ℃, have the structure of the end chain alkyl of 1～8% quality by softening temperature 20-80 ℃;

Said solidifying agent is the organic solvent that contains polyisocyanate prepolymers;

Polyisocyanate prepolymers is isocyanic ester and the ratio reaction products therefrom of TriMethylolPropane(TMP) by following molar weight: isocyanic ester: TriMethylolPropane(TMP)=3: 1;

Said organic solvent is selected from a kind of or its mixture in ethyl acetate, toluene or the butanone.

2. dry type compound polyurethane adhesive according to claim 1 is characterized in that, the weight concentration of polyester polyol is 50-80% in the organic solvent.

3. dry type compound polyurethane adhesive according to claim 1 and 2 is characterized in that, the weight concentration of isocyanate prepolymer is 50-75% in the organic solvent.

4. according to the preparation method of claim 1,2 or 3 described dry type compound polyurethane adhesives, it is characterized in that, comprise the steps:

(1) preparation of polyester polyol:

With two or more diprotic acid, one or more dibasic alcohol, one or more trifunctional acid or alcohol, one or more the acid of long alkyl chain simple function group or alcohol in the presence of catalyzer, the vacuum fusion polycondensation, temperature of reaction is 160-250 ℃, total reaction time is 20～30 hours, alcohol is 1.05-1.5 with the ratio of the total yield of acid: 1, obtain polyester polyol;

The catalyzer that uses is selected from a kind of in tetrabutyl titanate, metatitanic acid four Virahol esters, antimonous oxide, antimony acetate, tin protochloride or the dibutyl tin laurate etc.;

(2) preparation of solidifying agent: isocyanic ester and TriMethylolPropane(TMP) were reacted 5～10 hours down at 50～90 ℃, and isocyanic ester with the ratio of the molar weight of TriMethylolPropane(TMP) is: [NCO]: [OH]=3: 1;

(3) polyester polyol and the solidifying agent that obtains is dissolved in organic solvent respectively, promptly obtains dry type compound polyurethane adhesive of the present invention.

5. the preparation method of dry type compound polyurethane adhesive according to claim 4 is characterized in that, select oneself a kind of in diacid, nonane diacid, sebacic acid, terephthalic acid, m-phthalic acid or the Tetra hydro Phthalic anhydride of diprotic acid.

6. the preparation method of dry type compound polyurethane adhesive according to claim 4 is characterized in that, dibasic alcohol is selected from ethylene glycol, 1, a kind of in 4-butyleneglycol, neopentyl glycol, 2-methyl propanediol or the Diethylene Glycol.

7. the preparation method of dry type compound polyurethane adhesive according to claim 4 is characterized in that, trifunctional acid or alcohol are selected from glycerine, TriMethylolPropane(TMP) or trimellitic acid 1,2-anhydride.

8. the preparation method of dry type compound polyurethane adhesive according to claim 4 is characterized in that, acid of long alkyl chain simple function group or alcohol are selected from lauric acid, stearic acid or isooctyl alcohol.