KR900004705B1 - Acrylic modified reactive urethane hot melt adhesive composition - Google Patents

Abstract

A solvent-free normally solid hot melt polyurethane adhesive composition which is solid at room temperature comprising: (a) 5 to 90% by weight of a urethane prepolymer prepared from the condensation plymerisation of a polyisocyanate and a polyol and having an isocyanate content of 0.25 to 15% and an isocyanate index greater than 1 and no more than 2; (b) 10 to 95% by weight of a low molecular weight polymer of ethylenically unsaturated monomers containing no active hydrogen; said hot melt adhesive formulation being characterised, in the absence of tackifiers and/ or plasticisers, by a viscosity of 3 to 50 Pa.s (3000 to 50000cps) at 120 deg.C.

Description

Melt adhesive composition of reactive urethane polymerized with acryl

The present invention is a pending application of pending US Pat. No. 859,539, filed May 5, 1986.

The present invention relates to a low viscosity reactive urethane melt adhesive composition in which a low molecular weight acrylic resin is added to improve cohesion and adhesion. According to one embodiment of the invention, the acrylic unit (s) is polymerized with the non-isocyanate component of the polyurethane prepolymer, and then the non-isocyanate component is reacted with a functional group of a suitable isocyanate to produce a plasticizer or It forms a melt adhesive composition having a suitable coating viscosity that does not require the addition of an adhesive.

Melt adhesives are 100% solids that do not contain or require any solvent. They are solid materials at room temperature, but when heated, they melt in liquid or fluid form and adhere to the substrate. Upon cooling, the adhesive regains its solid form and restores cohesion. In this respect, the melt adhesive is different from other types of adhesives that adhere to a solid state by evaporating or removing the solvent or polymerizing.

To achieve the desired physical properties, most melt adhesives are melted at high temperatures in thermoplastics to form, cool and bond rapidly. Unfortunately, their thermoplastic properties are also heat sensitive, resulting in bonds that are broken even when exposed to weak heat. The melt adhesive composition applied in the molten state becomes solid upon cooling and continues to be cured by chemical crosslinking formed using a specific thermosetting material such as polyurethane. These melts exhibit excellent heat resistance but lack inherent strength and have in common with heavy balsams or greases before crosslinking. In addition, these polyurethanes, based on melt adhesives, lack adequate adhesion to many commercially available substrates such as polyvinyl chloride film, mylar (mglar) and aluminum. Attempts have been made to improve the initial adhesion of polyurethane melts by adding certain thermoplastics, for example as disclosed in Uchigaki et al., US Pat. No. 3,931,077, issued Jan. 6, 1976. However, since these thermoplastic resins are generally high molecular weight materials (for example, about 100,000 or more), the addition of these resins significantly increases the coating viscosity of the adhesive, so that the viscosity of the thermoplastic resin is sufficiently reduced to facilitate its use. Make it necessary to add. While lowering the thermal viscosity of the prepared adhesive, the addition of relatively large amounts of such plasticizers or pressure-sensitive adhesives has a detrimental effect on the adhesive properties of the polyurethane melt, especially after the bond has matured.

It is therefore an object of the present invention to provide an improved polyurethane melt adhesive composition characterized by having good initial adhesion to a wide range of conventional substrates as well as heat resistance even after aging of the bond.

They found that the addition of urethane polymers to low molecular weight polymers formed from urethane units to low molecular weight polymers formed from monomers distributed in ethylene form without containing active hydrogen resulted in solids at room temperature and additional plasticizers or adhesives. It is possible to easily coat at a viscosity of 3000 to 50,000 cps at 120 ° C. without the need to provide a melt adhesive having improved initial cohesion as well as improved strength after aging of the hardened bond. Moreover, the adhesive exhibits these improved properties for a wide range of substrates including difficult to bond substrates such as polyvinyl chloride, mylar (polyester film sold by Dupont) and aluminum.

Low molecular weight polymers may be added to the polyol prior to reacting with isocyanates or may be added to preformed prepolymers. The product of the present invention may be formed by simultaneously polymerizing the urethane prepolymer and the unsaturated units in ethylene form. Polyurethane prepolymers are also polymerized to be pressured in unsaturated units in ethylene form to continuously form the inventive formulations. In addition, monomers unsaturated in ethylene may be polymerized into polyols using a polymerization method of free groups. In this embodiment, the isocyanate component is continuously polymerized into the mixture using conventional condensation polymerization methods. This condensation polymerization method has the advantage of excellent control of the molecular weight (measured by high viscosity) of the vinyl polymer obtained, and also produces a polymer free of harmful impurities. It also results in significant cost savings due to the reduction of material handling and storage and the elimination of intermediate packaging and storage.

Ethylene-type unsaturated units capable of free radical polymerization and containing no active hydrogen may be used here. Among the most common uses are acrylic acid and methacrylic, including but not limited to methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate or iso-propyl, as well as the corresponding methacrylic-labels. There is an ester of C ₁ to C ₁₂ of the acid. Mixtures of compatible (meth) acrylate units can also be used. Such mixtures comprising butyl methacrylate and methyl are known in the art. Unsaturated monomers in the form of additional ethylene such as vinyl esters (such as vinyl acetate and vinyl propionate), vinyl ethers, fmarates, maleates, styrenes, acrylonitriles, ethylene, vinyl ethers, etc. may be used as their copolymers. have. In particular the choice of unit (s) will depend primarily on the end user required of the adhesive. For example, one of ordinary skill in the art will recognize that the choice of a unit can produce a pressure sensitive adhesive while the other unit produces a non-pressure sensitive material. Similarly, suitable units may be selected to make structural adhesives, conductive adhesives, and the like.

Urethane prepolymers are those commonly used to prepare polyurethane melt adhesive compositions. Generally, the prepolymers are prepared by condensation polymerization of polyisocyanates and polyols, preferably by polymerizing diisocyanates with diols. Polyols used include polyhydric ethers (substituted or unsubstituted polyalkene ether glycols or polyvalent polyalkylene ethers), polyhydric polyesters, ethylene or propylene oxides of polyols and mono-substituted esters of glycerol.

Suitable organic polyisocyanates include, for example, ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, cyclopentylene-1,3- Diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-di Isocyanate, diisocyanate P-phenylene, diisocyanate m-phenylene, diisocyanate xylene, diisocyanate 1,4-naphthylene, diisocyanate 1,5-naphthylene, diphenyl-4,4 '-Diisocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexaethylene diisocyanate, diisocyanate pulpylidene, 1-chlorobenzene-2,4-di Isocyanate, 4,4'4 ''-triisocyanato-triphenylmethane, 1,3,5 Such as -triisocyanato-benzene, 2,4,6-triisocyanato-toluene, 4,4'-dimethyldiphenylmethane-2,2'5,5-tetraisocyanate and the like.

The polyisocyanate and polyol component are combined in proportions to obtain a urethane prepolymer characterized by an isocyanate content of about 0.25 to about 15%, preferably about 10%. In addition, the ratio of isocyanate equivalents to hydroxyl equivalents (known as isocyanate index) should be greater than 1 but less than 2. By keeping the isocyanate index low, the level of free isocyanate content in the final melt adhesive composition can be lowered to about 4% or less, preferably 1% or less. It can be appreciated that the presence of high levels of free isocyanates has a detrimental effect on the formulation of the melt due to the emission of toxic gases when heated to the temperature at which the adhesive is used. In addition, when the free isocyanate is at a high level, the viscosity decreases, thereby lowering the initial bonding strength of the adhesive. The exact polyol equivalent of the polyisocyanate used in the polymerization reaction depends on the amount of polyol and the particular polyisocyanate used. In general, the amount of polyisocyanate needed to achieve the isocyanate content varies from about 5 to 55% of the final copolymer.

According to the broad scope of the present invention, the unsaturated unit in the form of ethylene may be polymerized at a relatively low molecular weight using a conventional polymerization method of free groups. For purposes of classification herein, "low molecular weight" means a molecular weight ranging from approximately 10,000 to 30,000. Low molecular weights are obtained by careful monitoring and control of the reaction conditions and generally by reaction in the presence of a chain transfer agent such as dodecyl mercaptan. There is a recognized correlation between intrinsic viscosity and molecular weight, and what they have found is that polymerization of monomers in general with intrinsic viscosity of 0.1 to 0.4 (measured with a 9: 1 mixture of IV tetrahydrofuran and alcohol) Particular preference for use. In this embodiment, the low molecular weight polymer is dissolved before mixing with the polyol and reacting with the isocyanate component or the low molecular weight polymer is dissolved in the urethane prepolymer already formed. In either case, the low molecular weight polymer is joined with a urethane prepolymer having isocyanate ends in a proportion such that the reactive cured melt adhesive comprises about 5 to 90% urethane prepolymer and 95% to 10% low molecular weight polymer. Care should be taken when storing and handling low molecular weight polymers to avoid contamination with atmospheric moisture or other factors that may affect the stability of the prepolymer system. And the obtained melt adhesive may be used as a molten form for the substrate to be bonded as a technique known to those skilled in the art. The urethane melt hardens with moisture in the air over time to form crosslinked network.

According to another method of preparing the urethane prepolymer of the present invention, an unsaturated unit in ethylene form is combined in an amount of about 2 to 90% by weight as 10 to 98% by weight of a polyol and a chain transfer agent such as dodecyl mercaptan It polymerizes in presence of the conventional method of superposition | polymerization of free group. After the polymerization of the unsaturated unit (s) in ethylene form, the polyisocyanate and any additional components required for the reaction to form the urethane prepolymer are added and this reaction is carried out using conventional condensation polymerization methods. In this process, the urethane prepolymer obtained with the isocyanate end groups forms the reactive curable melt adhesive as described above, which has 5 to 90% urethane prepolymer and low molecular weight of 95 to 10%, which is used for the substrate in molten form. Over time, it hardens with moisture in the air to form a crosslinked network.

It is also possible to polymerize low molecular weight polymers in the presence of urethane prepolymers with end groups of isocyanates already produced. This method has the drawback of unnecessarily heat-treating the prepolymer during the acrylic polymerization reaction, which causes side chaining, increased viscosity, consumption of necessary isocyanate groups and possibly gelation. Even if this drawback is controlled, it is necessary to control the adjustment more precisely than the polymerization reaction of the non-isocyanate functional group with the urethane component. When this reaction is carried out in polyols or other non-isocyanate-containing components, there is also the advantage that the reactant viscosity is lowered and the required heating amount is reduced, thereby reducing the exposure to isocyanate vapor.

As mentioned above, the obtained melt adhesive that is solid at room temperature has a suitable coating viscosity in the range of 3000 to 50,000 cps at 120 ° C. (which corresponds to about 1500 to 25000 at 135 ° C. and 10,000 to about 100,000 at 108 ° C.). There is no need for additional pressure sensitive adhesives and / or plasticizers to achieve such coverage viscosities. However, it should be noted that a small amount of the adhesive or plasticizer may be added so long as it does not adversely affect the required adhesive properties.

The adhesive not only hardens to form strong heat resistant bonds, but also exhibits high initial adhesion and cohesion, making it easy to handle and further process the bonded structure even before curing. As such, they are widely used in applications where melt adhesives are commonly used, including but not limited to, but not limited to, red pests, bookbinding, labeling of bottles and mail, assembly of automobiles, assembly of medical nonwoven products, and the like. It is easily used for applications that have a high degree of heat resistance that can be considered in non-integrated treatment or sterilization operations.

This superior property on the one hand can be assumed to be due to the formation of semi-interpenetrating and interpenetrating network as well as in some cases the formation of graft copolymers. Semi-interpenetrating networks are formed when a urethane prepolymer (thermoset) is used as a polymer polymerized with a free group containing no crosslinking group- (thermoplastic). When the polymer polymerized with the free group includes a crosslinking group, all interpenetrating networks are formed. Grafts are formed of urethane prepolymers of any type of functional group, such as including carbon atoms with tertiary hydrogen. These tertiary hydrogen atoms have potential graft positions for acrylic or vinyl units.

The present invention will be described in more detail below as examples of the preferred embodiments thereof, but such embodiments are included for illustrative purposes only and are not intended to limit the scope of the present invention unless otherwise specified.

Example 1

The reaction vessel of 1 liter capacity was equipped with a condenser, gas inlet tube, slow addition tube, thermometer, stirrer and heating / cooling device. The components of the reaction include:

The reaction vessel is blown with dry nitrogen and dry nitrogen is allowed to flow slowly, creating bubbles on the surface during the reaction. Components 1,2,3,4,6,8 and 9 are added to the vessel and the temperature is raised to 80 ° C. After 1/2 hour at 80 ° C., components 5 and 7 are added uniformly over 1 hour. The reaction is held again at 80 ° C. for 3 hours at which time component 10 is added. The reaction is held at 80 ° C. for another 2 hours and component 11 is added. The temperature is then raised to 100 ° C. and maintained for 3 hours. At this point, a 120 mm to 130 mm vacuum is applied to the vessel for 20 to 30 minutes and the reaction is poured hot from the flask.

Example 2

The experiment is carried out as in Example 1, in which case, as an alternative to reducing the molecular weight of the methacrylate resin, the molecular weight of the urethane tripolymer is lowered to lower the viscosity of the system. All arguments are the same except for the following:

TABLE 1

The properties are as follows:

Example 3

This example combines 70% polypropylene glycol having a molecular weight of 1000 and 30% of 1,6-hexanediol neopentyl glycol adipatediol having a molecular weight of 2000 with a sufficient amount of methylene bisphenyl diisocyanate to give an NCO content of 2 in the prepolymer. Disclosed is the preparation of a urethane prepolymer of%.

Way:

The 1 liter reaction vessel was equipped with a condenser, gas inlet tube, thermometer, stirrer, and heating and cooling system. The reaction vessel is blown with dry nitrogen and passed through in small quantities. Polyol is added to this reaction vessel and the temperature is raised to 80 ° C. At this point diisocyanate is added and the reaction is heated to 100 ° C. and maintained at this temperature for 4 hours. After 4 hours of heating, the reaction is poured out of the reaction vessel.

Example 4 (comparative)

This example describes the preparation of a melt adhesive using a mixture of polyurethane prepolymers, thermoplastics and adhesives in accordance with US Pat. No. 3,931,077.

The urethane prepolymer is placed in a three-neck flask and heated to 167 ° F. in a nitrogen atmosphere, and two additional ingredients are added and stirred in a nitrogen atmosphere until dissolved. This adhesive is referred to as IVA.

10 parts of Exxon EX 170 (25% vinyl acetate, 75% ethylene with a melt index of 2400); A second melt adhesive (referred to as IVB) was prepared as above using 25 parts PRL-300 and 65 parts of the urethane prepolymer of Example 3.

[exam]

In order to know the properties of the adhesives of the present invention and measure their efficacy, a series of tests were developed as follows. Tensile and Elongation of Cured Glass Films: This test measures the strength of a film and its elasticity. This tensile strength and elongation are related to the usefulness of the material as an adhesive. In general, materials with high tensile strength and adequate elongation are shown to have better adhesive performance than one or both of which are insufficient.

In this test, the film runs in a molten state to a low energy surface of approximately 3-5 mils thick (this range of film is used as a heavy film with excess cavities formed upon curing). The film is cured by exposure to air at constant temperature for one week at 22 ° C and 50% relative humidity.

Adhesion test: Samples were fabricated by using a variety of flexible substrates, coated with 1.0 mil melt adhesive, laminated onto a 3/8 '' particle plate on top of this laminate, and cold-pressed for 10 minutes at a mass of 5 psi. It was. All samples are left to cure for one week to cure or crosslink. This was then subjected to a 90 ° stripping test at a withdrawal rate of 120 inches.

Heat Resistance: Since most melts are thermoplastic and deform or leak when treated at temperatures above 82 ° C, they have conducted a series of shear tests at high temperature to measure outflow or deformation at temperatures up to 175 ° C.

In this test, a 1 mil thick adhesive is applied to a 3/8 '' particle plate to use a lapshear that covers 5 mil of bare aluminum foil. All samples are cured for one week.

The sample is placed in an air-circulated oven at 108 ° C. and subjected to a load of 1 kg / in ₂ . Hold at this temperature for 15 minutes, then raise the temperature to 120 ° C, observe for 15 minutes and raise the temperature at normal intervals until the next breakage is seen.

Ginger strength: This test measures the bonding strength immediately after application of the adhesive and bonding. This is important because it tests the uncured strength of the material before it is cured. Sufficient ginger is required to hold the substance to the substrate during curing with moisture in the atmosphere. Ginger before hardening and immediate bonding force, as well as curing speed, are very important for assembly and lamination processes before they are fully cured.

In this test, a 2 mil mylar film was precisely coated with a 1.0 mil thick adhesive sample at 120 ° C. and immediately covered with a 5 mil aluminum foil. The resulting mylar / adhesive / foil laminate was deprived immediately and after a defined time at a rate of 12 inches / minute with an Instron tester.

In Examples 3 and 4, the tensile strength is low, and in Examples 1 and 2 of the present invention, the tensile strength is increased and the elongation is good. It can also be seen that the high tensile strength of Example 2 correlates with the high NCO content.

Examples 1 and 2 both showed good binding to most substrates and Example 1 showed good adhesion to all substrates including Mylar. The failure recorded was FT (fiber tearing). This adhesive was applied to the top fibers of the particle plate substrate. Example 2 lacked adhesion only to Mylar. Example 3 lacked adhesion to foil and mylar; Mylar and Vinyl in Example 4A and Mylar in Example 4B

This test accounts for the poor heat resistance of Examples 4A and 4B (an example of prior art) and the good heat of Examples 1 and 2, and especially Example 2, which is in the form of a high NCO content, shows the best heat resistance.

The above test results show excellent properties for the acrylic-free prepolymer melts of the present invention and the materials disclosed in US Pat. No. 3,931,077 with regard to the bonding strength and heat resistance after special aging.

The following examples incorporate the modifications of their most preferred embodiments to illustrate various features of the invention.

Example 5

The method of Example 1 was repeated except that 0.8 gm of dodecyl mercaptan was used instead of 0.68 gm. This change is intended to reduce the molecular weight (as indicated by the low intrinsic viscosity) of the methacrylate copolymer portion in this product and thus reduce the viscosity of this product.

The properties are as follows:

Example 6

In order to increase the viscosity by increasing the molecular weight of the methacrylate polymer than in Example 2 was carried out as in Example 1 except that the dodecyl mercaptan chain transfer agent was reduced to 0.54gm.

The properties are as follows:

Example 7

The following examples illustrate changes of Example 1 to the following important aspects:

1) Changed ratio of methacrylate polymer to urethane tripolymer from 25/75 to 30/70.

2) Change the ratio of butyl methacrylate to methyl methacrylate from 64/36 to 80/20.

3) Change the composition of the urethane prepolymer from polypropylene glycol / 1,6-hexanediol, neopentyl glycol adipate-methylene bis phenyl diiso cyanate to polypropylene glycol-methylene bis phenyl diisocyanate.

This Example was carried out as in Example 1 except that the following amounts were used.

Example 8

The examples below illustrate the use of different acrylate units. This Example was carried out as in Example 1 with the following components.

Example 9

In this example, isocyanate was used instead of methylene bis phenyl diisocyanate. This example was carried out as in Example 1 with the components shown below.

Example 10

In this example, a catalyst was added to increase the curing rate. And it implemented using the method of Example 1.

Example 11

In this example, the method of Example 1 was repeated replacing the acrylate comonomer with styrene. Ingredients and properties are as follows.

Example 12

Again, the acrylate copolymer was replaced with vinyl acetate and the method of Example 1 was repeated. Ingredients and properties are as follows.

Example 13

This example illustrates the addition of commercially available low molecular weight polymers to a urethane prepolymer to prepare a melt adhesive in accordance with another embodiment of the present invention. Elvacite 2013 is a copolymer of 64% butyl methacrylate / 36% methyl methacrylate, commercially available from Dupont I.V, 0.2. The Elvacite was vacuum dried in a dryer for 24 hours immediately before use.

Way:

This polyol and Elvacite 2013 are added to the vessel and heated to 100 ° C. until the Elvacite is dissolved. At this point methylene bis phenyl diisocyanate was added and the reaction held at 100 ° C. for 3 hours. After holding for 3 hours at 100 ° C., the reaction is poured off the vessel into a hot state. This sample has the following properties:

Example 14

Initial (raw) tensile strength properties were made for comparison purposes, according to the present invention, additional adhesives (referred to as 1 to 4) were prepared using the method described above. Five different adhesives were prepared according to Examples 2,3,4,5 and 9 (referred to as 5-9, respectively) of US Pat. No. 3,968,089 to Cuscurida et al. The components and amounts of the raw materials used are shown in Table 1. Intrinsic viscosity, isocyanate index and viscosity at room temperature are shown in Table 2.

TABLE 2

The following test method was used to measure the initial (raw) strength of the adhesive. The results of this test are shown in Table 3.

[Skimping test]

A wood-grained vinyl substrate is coated (approximately or mobile) with an adhesive heated to approximately 120 ° C. to a thickness of 1.0 to 1.5 mils, attached to a 3/8 '' thick particle plate and pressured at 5 pounds. Pressed for 3-5 seconds. This sample was stripped at 90 ° at a rate of 5 '' / min with a stripping test key such as an Instron tester as an example (sample dimension = 1/2 '' wide strip, 3-4 '' wide). This sample was stripped immediately after pressing, for example, 1-2 minutes.

[Lap Shear]

5 mil gauge aluminum was coated (directly or mobile) with a thickness of 2-3 mils with an adhesive heated to approximately 120 ° C. The coated aluminum was covered with a 3/8 '' particle plate and pressed for 3-5 seconds at a pressure of approximately 5 pounds. This sample was pulled at 180 ° C. at a rate of 0.2 inches of segmentation in a tensile strength tester (eg Instron tester) (sample dimensions of 1/2 '' x 1/2 '' mating area). This sample was pulled immediately after compression, for example 1-2 minutes.

TABLE 3

It is apparent here that changes or modifications can be made to the above-described embodiments of the present invention without departing from the scope of the present invention as defined by the claims, and therefore all matters contained in the above specification are intended to limit Rather, the other is presented for the purpose of explanation.

TABLE I

Claims (17)

a) 5 to 90 weight percent of a urethane prepolymer containing 0.25 to 15% isocyanate, having an isocyanate index greater than 1 and not greater than 2 and prepared by condensation polymerization of isocyanate and polyol; b) 10 to 95% by weight of a low molecular weight polymer of ethylenically unsaturated units, free of active hydrogen; The melt adhesive formulation described above has a viscosity of 3000 to 50,000 cps at 120 ° C. in the absence of adhesive and / or plasticizer; A hot melt polyurethane adhesive composition that is solid at room temperature and contains no solvent. The monomer of claim 1, wherein the monomer unsaturated in ethylene form is selected from C ₁ to C ₁₂ esters of acrylic and methacrylic acid, vinyl esters and ethers, fmarates, maleates, styrene, acrylonitrile, ethylene and mixtures thereof. A melt adhesive composition selected from the group comprising. The melt adhesive composition of claim 1, wherein the urethane prepolymer is prepared by condensation polymerization of diols and diisocyanates. The melt adhesive composition of claim 1, wherein the unsaturated monomer in ethylene form is polymerized to an inherent viscosity of 0.1 to 0.4. The group according to claim 1, comprising polyalkylene ether glycols with or without polyols substituted or polyvalent polyalkylene ethers, polyvalent polyesters, ethylene or propylene oxide adducts of polyols and mono-substituted esters of glycols Selected melt adhesive composition from. The polyisocyanate according to claim 1, wherein the polyisocyanate is ethylene diisocyanate, ethyl isocyanate diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, cyclopentylene-1,3- Diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-di Isocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, diphenyl-4,4'-diisocyanate, Azobenzene-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, fulfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4,4 ' , 4 ''-triisoanato- Riphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,6-triisocyanato-toluene and 4,4'-dimethyldiphenylmethane-2,2 ', 5,5-tetraisocyanate Melt adhesive selected from the group comprising. The melt adhesive of claim 1, wherein the free isocyanate content is 4% or less. 8. The melt adhesive of claim 7, wherein the free isocyanate content is 1% or less. Polyurethane tripolymers having isocyanate end groups comprising low molecular weight polymers of resins contained in ethylene form in the tripolymer, wherein the polyurethane prepolymer having isocyanate end groups has an isocyanate content of 0.25 to 15% and at least one 2 Has an isocyanate index of the following; The adhesives described above comprise 1) 2 to 90% by weight of active hydrogen-free and ethylenically unsaturated units and 10 to 90% by weight of polyols; 2) polymerizing the mixture (1) using a free radical polymerization method as chain transfer agents to obtain a low molecular weight polymer; 3) Solvent-free molten adhesive composition prepared by the step of adding a sufficient amount of polyisocyanate to this to obtain required isocyanate content and isocyanate index and polymerizing using condensation polymerization method, which is solid at room temperature. 10. The monomer of claim 9, wherein the unsaturated units in ethylene form comprise C ₁ to C ₁₂ esters of acrylic and methacrylic acid, vinyl esters and ethers, fmarates, maleates, acrylonitrile, ethylene and mixtures thereof. Melt adhesive composition selected from the group. 10. The melt adhesive composition of claim 9, wherein the urethane prepolymer is prepared by condensation polymerization of diol and diisocyanate. 10. The melt adhesive composition of claim 9, wherein the unsaturated monomer in ethylene form is polymerized to an intrinsic viscosity of 0.1 to 0.4. 10. The group according to claim 9, wherein the polyol is substituted or unsubstituted polyalkylene ether glycols or polyvalent polyalkylene ethers, polyvalent polyesters, ethylene or propylene oxide adducts of polyols and groups containing mono-substituted esters of glycols Melt adhesive composition selected from. The polyisocyanate according to claim 9, wherein the polyisocyanate is ethylene diisocyanate, ethyl isocyanate diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diocyanate, cyclopentylene-1,3- Diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenyl propane-4,4'-di Isocyanate, p-diphenylene diisocyanate, m-phenylene diisocyanate, diisocyanate xylene, 1,4-taphthylene diisocyanate, 1,5-naphthylene diisocyanate, diphenyl-4,4'-di Isocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4 , 4 ', 4' '-triisocyanato- Riphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,6-triisocyanato-toluene and 4,4'-dimethyldiphenylmethane-2,2 ', 5,5-tetraisocyanate Melt adhesive selected from the group comprising. 10. The melt adhesive of claim 9, wherein the free isocyanate content is 4% or less. 17. The melt adhesive of claim 16, wherein the free isocyanate content is less than or equal to 1%. 1) 2 to 9 weight percent of monomers unsaturated in ethylene form and 98 weight percent of polyols without active hydrogen; 2) polymerizing the mixture (1) using a free radical polymerization method as a chain transfer agent to obtain a low molecular weight polymer; 3) adding a sufficient amount of polyisocyanate thereto to obtain an isocyanate content of 0.25 to 15% and an isocyanate index of 1 or more and 2 or less and polymerizing it using a condensation polymerization method; A method for producing a molten polyurethane adhesive composition containing no solvent which is a solid at room temperature, characterized by a viscosity of 3000 to 50,000 cps at 120 ° C. without adding an adhesive or a plasticizer.