KR100506548B1 - Hot Melt Adhesives for Disposable Products and Products Prepared therefrom - Google Patents

Abstract

The present invention relates to hot melt adhesive compositions containing high molecular weight linear styrene-isoprene-styrene block copolymers or high amounts of linear styrene-butadiene-styrene copolymers, containing very little or no residual double blocks, and thus To a manufactured product. The resulting adhesive composition may contain a solid viscosity resin and a liquid viscosity resin.

Description

Hot Melt Adhesives for Disposable Products and Products Prepared therefrom

The present invention relates to a hot-melt adhesive (HMA) for use in the manufacture of disposables. More specifically, the present invention comprises a high molecular weight linear styrene-isoprene-styrene (SIS) block copolymer or a high molecular weight linear styrene-butadiene-styrene (SBS) copolymer having a respective minimum polystyrene block molecular weight of 18,000. It relates to a hot melt adhesive formulation. In addition, the linear SIS and SBS copolymers are preferably prepared by a continuous polymerization process which produces little or no residual double blocks. SIS or SBS block copolymers are blended with solid tackifying resins and optionally liquid tackifying resins or plastic oils to create a hot melt adhesive. The present invention also relates to the manufacture of disposable articles in which the new hot melt adhesive formulations are used to bond polyethylene or polypropylene substrates to tissues or nonwovens, or to attach elastic bands to tissues or nonwovens.

The preparation of hot melt adhesive compositions from SIS block copolymers and SBS block copolymers is well known in the art. Due to the various features involved in successful hot melt adhesives, some hot melt adhesives may be useful in one particular application and another may be useful in a second application. Additionally, hot melt adhesives of block copolymers may be required for bonding between substrates formed from different materials such as plastics and the like. In the process of disposable articles, such as disposable diapers, sanitary napkins, bed pads, and the like, the manufacture of such articles generally employs the use of hot melt adhesives that can be bonded at relatively low temperatures in order to avoid damage to one of the other substrates in the disposable article. in need.

For example, in disposable articles such as diapers, the hot melt adhesive should be able to bond the moisture absorbent nonwoven to the substrate via a continuous or discontinuous film in order to bond the moisture absorbent nonwoven to the substrate. In addition, in disposable diapers, the nonwoven is generally bonded to the inside of the soft material for core stabilization. Hot melt adhesives can be used between the outside of the moisture impermeable material and the soft surface material to minimize moisture.

In the manufacture of such disposables, the disposables can be made by applying a hot melt adhesive via extrusion, spraying or multi-line technology, and one of several formulation methods has been commonly practiced in the art. The first method is to provide tackifying resins and oils with relatively low molecular weight linear styrene-isoprene-styrene or styrene-butadiene-styrene copolymers in the formulation, the formulations generally containing 15 to 35% by weight of block copolymers. do. One example of such a formulation is described in US Pat. No. 5,149,741, wherein the multipurpose adhesive composition for hot melt adhesives comprises about SIS block copolymers (containing 25 weight percent styrene in the total block copolymer). Parts by weight, about 60 parts by weight of pentaerythritol ester, about 15 parts by weight of naphthenic / paraffin mineral oil, and 0.1 to 2.0 parts by weight of a blend of phosphite antioxidants, hindered phenolic antioxidants and thioester potentiators, respectively It contains. In such formulations, the styrene content of the SIS copolymer is 25 to 50% by weight based on the total weight of the copolymer and the molecular weight of the SIS copolymer is relatively small. In addition, the adhesive composition described above contains 15 to 40% by weight of SIS.

The second process comprises tackifying resins and oils with relatively high molecular weight radial or multibranched styrene-butadiene or styrene-isoprene block copolymers having the formula: in hot melt formulations containing only 5-14% by weight of block copolymers. Is to use:

(A-B) _n -Y

In the above formula,

Y is a polyvalent coupling agent,

A comprises an aromatic block (eg styrene) substituted with polyvinyl,

B comprises a polymerizable rubbery intermediate block (eg isoprene or butadiene),

n is an integer of 3 or more.

The advantage of this method is described in US Pat. No. 5,057,571, for example, in which the block copolymer, the most expensive component in the hot melt adhesive compound, is used at a low level, thereby lowering the price of the hot melt formulation. As described in US Pat. No. 5,057,571, 5-14% of the radial block copolymer of the molecular weight described above was used at low levels using a radial block copolymer having a molecular weight greater than about 140,000 and preferably greater than 160,000. The quality required for the hot melt adhesive having can be obtained. H. ratio. U.S. Patent No. 5,037,411, entitled “Disposable Article Multi-Line Construction Adhesive,” assigned to HB Fuller Company, also includes 5 to 15 weight percent radial copolymer. Disposable articles using a hot melt pressure sensitive adhesive composition comprising tackifying resins, plastic oils, petroleum derived waxes and stabilizers that can be used are described. In one example cited in US Pat. No. 5,037,411, Table (4) compares an adhesive made from a linear multiblock ABABAB copolymer with an adhesive made from a high molecular weight radial block copolymer as presented herein. . As indicated in this patent, the data clearly show that adhesives prepared using radial copolymers at levels up to 15% differ from, and are superior to, conventional adhesives having greater than 15% by weight of polymer in the adhesive formulation. .

However, it is useful for the assembly of disposable products such as diapers, bed pads and women's protective pads, in which the very high molecular weight linear SIS or SBS block copolymers in the hot melt formulations are at somewhat lower formulation levels, ie 15% by weight of the block copolymers. There is still a need for improved hot melt adhesive compositions that are formulated below to enable low rubber formulations compared to conventional hot melt adhesives based on low molecular weight linear SIS and SBS block copolymers.

It is therefore an object of the present invention to meet these and other needs.

In particular, it is an object of the present invention to provide a novel high molecular weight linear ABA block copolymer (where A is a polystyrene block and B is a rubbery conjugate) in an improved hot melt formulation which is useful for the assembly of disposables, especially multi-lined disposables. Diene blocks, for example isoprene or butadiene).

Another object of the present invention is to use a high molecular weight linear block copolymer at a very low level, it is excellent in heat resistance, low viscosity and excellent in stopping time, good peel adhesion, It is to provide a hot melt adhesive composition having good viscosity and a high ability to bind to a substrate at a temperature lower than the temperature at which the polyethylene or polypropylene substrate is damaged.

Another more specific object of the present invention is a disposable article, in particular a diaper, wherein a polyethylene or polypropylene substrate is bonded to a tissue, or a nonwoven polyethylene or polypropylene substrate, or both by means of the improved hot melt adhesive composition described above. To provide a product of a multi-line structure, such as bed pads and women's protective pads.

Another more specific object of the present invention is to provide an improved hot melt adhesive composition which results in lower production costs by using significantly smaller amounts of high molecular weight linear block copolymers in HMA formulations.

In a preferred embodiment of the invention, the high molecular weight linear SIS and SBS copolymers are produced by a continuous polymerization process (A-B-A is polymerized continuously) so that the final copolymer product contains little or no residual double blocks.

Block copolymer polymerization method

As is well known, polymers containing both aromatic and ethylenically unsaturated compounds copolymerize one or more polyolefins, in particular diolefins in this case isoprene or butadiene, with one or more alkenyl aromatic hydrocarbon monomers in this case styrene. Can be prepared by Of course, the copolymer may be irregular, tapered blocks or combinations thereof, in this case blocks. The blocks in the copolymer of the invention are linear.

Polymers containing ethylenically unsaturated compounds or containing both aromatic and ethylenically unsaturated compounds can be prepared using free radicals, cationic and anionic initiators or polymerization catalysts. Such polymers may be prepared using bulking, solution or emulsification techniques. In any case, polymers containing at least ethylenically unsaturated compounds will generally be recovered as solids such as flours, powders, pellets and the like. Of course, polymers containing ethylenically unsaturated compounds and polymers containing both aromatic and ethylenically unsaturated compounds are commercially available from various suppliers.

Copolymers of conjugated diolefin polymers and one or more conjugated diolefins and one or more alkenyl aromatic hydrocarbon monomers, such as predominantly linear S-I-S or S-B-S block copolymers, are often prepared in solution by anionic polymerization techniques. In general, when using anionic techniques in solution, these SIS or SBS block copolymers can be prepared by simultaneously or in combination with the organic alkali metal compound the monomers to be polymerized at about 150 to about 300 ° C., preferably at about 0 to about 100 ° C., in a suitable solvent. It is produced by continuous contact. Particularly effective anionic polymerization initiators are organolithium compounds having the formula:

RLi _n

In the above formula,

R is an aliphatic, cycloaliphatic, aromatic or alkyl substituted aromatic hydrocarbon radical having 1 to about 20 carbon atoms,

n is an integer of 1-4.

In general, any solvent known in the art to be useful for preparing the polymer may be used. Suitable solvents include alkyl substituted derivatives thereof in addition to straight and branched chain hydrocarbons such as pentane, hexane, heptane, octane and the like; Alkyl substituted derivatives thereof in addition to cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane and the like; Aromatic and alkyl substituted aromatic hydrocarbons such as benzene, naphthalene, toluene, zylene and the like; Hydrogenated aromatic hydrocarbons such as tetralin, decalin and the like; Linear and cyclic ethers such as methyl ether, methyl ethyl ether, tetrahydrofuran and the like.

The concentration of initiator can be adjusted by controlling the molecular weight of the overall composition and the polystyrene block. Generally, the concentration of initiator is about 0.25 to about 50 mmoles per 100 grams of monomers. The ratio of initiator to monomer determines the block size, i.e., the higher the ratio of initiator to monomer, the smaller the molecular weight of the block.

Methods of controlling the molecular weight of blocks and total polymers are fairly well known. For example, such methods are described in US Pat. No. 3,149,182, US Pat. No. 3,231,635, and many other references, which are incorporated herein by reference, in which the amount of monomers can be kept constant and different. It is mentioned that the molecular weight can be achieved by varying the amount of organic lithium initiator, or that the amount of initiator catalyst can be kept constant and that different molecular weights can be achieved by changing the amount of monomer.

The first step of this process involves contacting the monoalkenyl arene with an organic monolithium compound (initiator) in the presence of an inert diluent to form an active polymeric compound with simple structure A-Li. Preferably, the monoalkenyl arene is styrene.

Next, the vigorous polymer in solution is contacted with the conjugated diene. Preferred dienes include butadiene and isoprene. The resulting vigorous polymer has a simple structure A-B-Li.

In this regard, two methods, one of (1) the coupling process or (2) the continuous process, can be used to produce the linear A-B-A triblock copolymer. In the coupling process, the vigorous A-B-Li polymer is coupled with the multifunctional coupling agent.

There are many coupling agents that can be used. Any multifunctional coupling agent containing two or more reactive sites can be used. Examples of this type of compound that may be used may include polyepoxides, polyisocyanates, polyimines, polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides, and the like. Such compounds may contain two or more functional groups, such as bonding epoxy and aldehyde groups, bonding isocyanates and halide groups, and the like. There may be various other substituents which are inert in the treatment reaction, such as hydrocarbon radicals such as alkyl, cycloalkyl, aryl, aralkyl and alkaryl groups, alkoxy, aryloxy, alkylthio, arylthio and tertiary amino groups. Many suitable types of such multifunctional compounds are described in US Pat. Nos. 3,595,941, 3,468,972, 3,135,716, 3,078,254 and 3,594,452. If the coupling agent has two reactive sites, such as dibromoethane, the polymer will have a linear ABA structure. If the coupling agent has three or more reactive sites, such as silicon tetrachloride, the polymer will have a radial or branched structure such as (AB) _n BA.

In the prior art as exemplified in US Pat. Nos. 3,595,941 and 3,468,972, the highest coupling efficiency has been achieved in an effort to always select a particular coupling agent or reaction condition. Coupling efficiency is the number of coupled polymer molecules divided by the number of coupled polymer molecules and the number of uncoupled polymer molecules. As such, when producing SIS linear polymers, the coupling efficiency is represented by the following relationship, where SI refers to a styrene-isoprene double block:

Coupling efficiency may in theory be measured from the stoichiometric amount of coupling agent required to complete the coupling, or may be measured by analytical methods such as gel permeation chromatography. Typically the coupling efficiency in the prior art is about 80 to about 100%.

Common coupling conditions include a temperature of about 65 to about 80 ° C. and a pressure sufficient to maintain the reactants in the liquid phase.

After the coupling reaction or when the desired coupling efficiency is obtained, the product is neutralized, for example, by the addition of terminators such as water, alcohol or other reagents, for the purpose of removing nucleating lithium radicals to the condensation polymer product. The product is then recovered, for example, by coagulation with hot water or steam or both, or by using vacuum devolatilization / extrusion.

Alternatively, the vigorous A-B-Li polymer may be reacted with a second addition of styrene monomer in a continuous polymerization process to produce a linear A-B-A triple block copolymer. This method has the advantage of leaving no measurable double blocks at all.

After the continuous polymerization, the product is terminated using hydrogen or by adding protic terminators, such as water, alcohol or other reagents, for the purpose of removing nucleating lithium radicals to the condensation polymer product. The product is then recovered, for example, by coagulation with hot water, steam or both, or by using vacuum devolatilization / extrusion. The polymer is not hydrogenated.

In a preferred embodiment of the invention, the linear A-B-A block copolymers used in the present invention contain more than 95% triple blocks. When A-B-A block copolymers are prepared using the coupling process described above, preferred embodiments of the present invention use A-B-A block copolymers having a coupling efficiency of greater than 95%. In the most preferred embodiment of the present invention, the linear A-B-A block copolymers used in the present invention are polymerized continuously according to the continuous method described above and contain more than 98% of the triple block copolymers.

The hot melt adhesive composition of the invention comprises in particular 5 to 15% by weight of high molecular weight linear SIS or SBS block copolymers or mixtures thereof, wherein the linear SIS block copolymer contains 25 to 35% by weight of styrene, The molecular weight is 120,000 to 200,000 and is adjusted for the composition. Linear SBS block copolymers contain 25 to 35 weight percent polystyrene, have a molecular weight of 100,000 to 180,000, and are adjusted for composition. Moreover, linear SIS and SBS block copolymers have a minimum polystyrene block molecular weight of about 18,000. In addition, the linear SIS and SBS block copolymers are preferably prepared in the continuous polymerization process described above and contain little or no double blocks. In addition, the linear SIS and SBS containing compositions comprise 45 to 85 weight percent of compatible solid tackifying resins and 0 to 35 weight percent of plastic oil or liquid tackifying resins.

Further, the hot melt adhesive is about 5 to 15% by weight, more preferably about linear ABA block copolymer (component B is polyisoprene and component A is polystyrene) based on the weight of the heat melt adhesive composition. The average molecular weight of the polystyrene block, comprising from 8 to about 13 weight percent and corrected for the composition of the polymer, is about 18,000 to 26,000, more preferably about 18,000 to 24,000 and most preferably about 18,000 to 22,000. The overall average molecular weight of the linear block copolymer, corrected for the composition of the polymer, is from about 120,000 to about 200,000, more preferably from about 125,000 to 180,000 and most preferably from about 125,000 to about 150,000, wherein the component A is a block copolymer From about 25 to 35 parts by weight, more preferably from about 28 to about 32 parts by weight, and based on the weight of the hot melt adhesive composition, about 45 to about 85 weights of the compatible solid tackifying resin % And about 0 to about 35 weight percent of a plastic oil or liquid tackifying resin based on the weight of the hot melt adhesive.

Alternatively, the hot melt adhesive is about 5 to about 15 weight percent, more preferably about 8 to about linear ABA block copolymer (component B is polybutadiene) based on the weight of the heat melt adhesive composition 13 weight percent, wherein the average molecular weight of the polystyrene block, corrected for the composition of the polymer, is about 18,000 to 26,000, more preferably about 18,000 to 24,000, and most preferably about 18,000 to 22,000, and is corrected for the polymer composition. The average molecular weight of the linear block copolymer is about 100,000 to about 180,000, more preferably about 110,000 to 160,000 and most preferably about 110,000 to about 140,000, and the component A is at least 25 to 100 parts by weight of the block copolymer. 35 parts by weight, more preferably from about 28 to about 32 parts by weight, wherein the adhesive also determines the weight of the hot melt adhesive composition About 45 to about 85 weight percent of compatible solid tackifying resins and about 0 to about 35 weight percent of plastic oil or liquid tackifying resins based on the weight of the hot melt adhesive.

Products using such novel hot melt adhesives are constructed by using extrusion, spraying, or multiple line type techniques to bond layers to a substrate, or bond elastic bands to a substrate, which methods are known in the art. have.

Molecular weights reported herein are molecular weights corrected for the composition of the polymer. The molecular weights quoted are not polystyrene equivalent molecular weights, but substantial molecular weights corrected for the composition of the polymer. Molecular weights are described in J.R. Runyon, et al., And J. Polym. Sci. 13,2359 (1969), L.H. Tung, J. Appl. Polym. Sci. 24, 953-963 (1979)] by gel permeation chromatography (GPC) using the method described.

A hot melt adhesive composition composed of a relatively high molecular weight ABA block copolymer, to which a primary tackifying resin, a secondary tackifying resin or a plastic oil, and a stabilizer are added, is a disposable article, in particular as a fine strip with vertically parallel adhesives, or Very suitable properties for the construction of disposable products in multi-line configurations that combine an outer moisture impermeable polyethylene or polypropylene sheet with an inner moisture absorbent sheet or tissue as applied as multiple dots of adhesive droplets and used as diaper components. It was found to have. Such a hot melt adhesive composition can be melted and then maintained at a temperature relatively lower than the high temperature under the entire nitrogen atmosphere without pyrolysis. The composition may be applied to the polyethylene and polypropylene substrates in a fluid form as a suitable continuous or discontinuous film in fine lines or multiple dot patterns, with no risk of damage to the polyethylene or polypropylene substrates. These hot melt adhesive compositions have also been found to act as constituents upon bonding with an outer sheet or cover that overlaps the absorbent pad as required in the manufacture of sanitary napkins. The hot melt adhesive composition applied as a fluid bonds and seals an absorbent pad located inside the outer sheet that penetrates the overlapped area and acts as a cover.

Tackifying Resin

Primary tackifying resins useful in the practice of the present invention include hydrocarbon resins, synthetic polyterpenes, resin esters, and natural terpenes, which are semisolid or solid at room temperature, generally from about 40 to about 135 ° C., preferably from about 70 to Soften or liquid at about 120 ° C. Examples of primary tackifying resins include (1) natural or modified rosins such as gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin; (2) Glycerol and pentaerythritol esters of natural and modified rosins, such as glycerol esters of pale, wood rosin, glycerol esters of hydrogenated rosin, glycerol esters of polymerized rosin, penta of hydrogenated rosin Erythritol esters, and phenolic modified pentaerythritol esters of rosin; (3) copolymers and trimers of natural terpenes such as styrene / terpene and alpha methyl styrene / terpene; (4) a polyterpene resin having a softening point of about 80 to 150 ° C., as measured by ASTM method E28-58T, which is generally present in the presence of Friedel-Crafts catalyst at moderately low temperatures Resulting from the polymerization of terpene hydrocarbons such as bicyclic monoterpenes known as pinene, and also include hydrogenated polyterpene resins); (5) phenolic modified terpene resins and their hydrogenated derivatives, such as resin products resulting from the condensation of bicyclic terpenes with phenols in acidic media; (6) aliphatic petroleum hydrocarbon resins having a ball and ring softening point of about 40 to 135 DEG C. (this resin is produced from the polymerization of monomers consisting primarily of olefins and diolefins; Resins); (7) aromatic petroleum hydrocarbon resins, and mixed aromatic and aliphatic paraffin hydrocarbon resins, and hydrogenated derivatives thereof; (8) aromatic modified alicyclic petroleum hydrocarbon resins and their hydrogenated derivatives; And (9) compatible resins such as cycloaliphatic petroleum hydrocarbon resins and their hydrogenated derivatives. Preferred primary tackifying resins for use in the practice of the present invention are representative of the resins of (8) and (9) above when the hot melt adhesive is formulated using SIS block copolymers, and the hot melt adhesive is an SBS block. When formulated using a copolymer, the resins of the above (2), (3) and (8) are typical. Suitable secondary tackifying resins are resins which are named materials in which the resin is liquid at ambient temperature.

Plastic oil

Various plastic oils are useful in the practice of the present invention. Plastic oils can be used in place of or in combination with secondary viscosity agents to reduce viscosity and improve tack. Plastic oils that have been found to be useful include vegetable and animal oils and derivatives thereof in addition to olefin oligomers and low molecular weight polymers. Petroleum derived oils that can be used are relatively high boiling materials which contain only minor amounts of aromatic hydrocarbons (preferably less than 30% by weight of the oil, more specifically less than 15% by weight). Alternatively, the oil may be wholly nonaromatic. The oligomers may be polypropylene having an average molecular weight of about 350 to about 10,000, polybutene, hydrogenated polyisoprene, hydrogenated polybutadiene, polypiperylene, copolymers of piperylene and isoprene, and the like. Vegetable and animal oils include glyceryl esters of common fatty acids and their polymerization products.

Stabilizers or antioxidants used in accordance with the practice of the present invention include high molecular weight hindered phenols and multifunctional phenols such as sulfur and phosphorus containing phenols. Hindered phenols are well known to those skilled in the art and can be characterized as their phenolic hydroxyl groups. In particular, tertiary butyl groups are substituted on the benzene ring at one or more of the ortho positions for the phenolic hydroxyl groups. The presence of such steric bulk substituted radicals adjacent to the hydroxyl group serves to inhibit the stretching frequency of the hydroxyl group and the reactivity of the corresponding hydroxyl group; This steric hindrance provides stabilizing properties to phenolic compounds. Representative hindered phenols include 1,3,5-trimethyl 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene; Pentaerythryl tetrakis-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate; 4,4'-methylenebis (2,6-tert-butylphenol); 4,4'-thiobis (6-tert-butyl-o-cresol); 2,6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2,4-bis (n-octylthio) -1,3,5 triazine; Di-n-octadecyl 3,5-di-tert-butyl-4-hydroxy-benzylphosphonate; 2- (n-octylthio) ethyl 3,5-di-tert-butyl-4-hydroxy-benzoate; And sorbitol [hex 3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate].

The hot melt adhesive composition is prepared for use by combining the ABA block copolymer with a primary tackifying resin, a secondary tackifying resin or a plastic oil, and a stabilizer in any order, or the materials are added together at the same time, The composition can be produced. In industrial practice, it is expected that primary tackifying resins and copolymers will be blended together at sufficiently elevated temperatures to produce fluid melts, with or without simultaneous addition of secondary tackifying resins or plastic oils, and stabilizers. For example, the copolymer can be blended with a compatible solid primary tackifying resin at a temperature of about 110 to about 200 ° C., preferably about 130 to about 180 ° C. to produce a fluid melt. Secondary liquid tackifying resins or plastic oils and stabilizers may then be added to the melt. Alternatively, the fluid melt may be prepared using all components of the adhesive composition present from the beginning.

In one embodiment of making the hot melt adhesives described above, the adhesive formulations were prepared in a sigma-blade heat melt compounding batch mixer, and the linear block copolymers were blended, melt compounded or in cyclohexane. After solvent blending, the mixture was premixed with 33% oil by weight plastic oil by vacuum devolatileing to produce an oiled block copolymer. Hot melt adhesive formulations generally consist of the following components:

In a preferred embodiment, after adjusting for the oil component of the oiled block copolymer, the formulation contains the following weight percent of the main component: block copolymer / tackifier / oil = 11% / 64% / 25 %. The melt mixer was then preheated to 340 ° F. Half of the tackifying resin and both Irganox 1010 were added and mixed for 2 minutes. Then all of the oiled block copolymers were added first and mixing continued for 4.5 hours. Tackifying resin residue was added and mixing continued for an additional hour. The oil was then added in 1/3 increments and mixed for 30 minutes after each addition. Polymer characterization and adhesive testing procedures are described in US Pat. Nos. 5,266,314 and 5,292,819, which are incorporated herein by reference.

In the adhesive tensile test of the hot melt adhesive formulation, a 0.062 inch thick plate of HMA is a compact formed in a chase between two release coated papers under pressure of 130 ° C. The molded plate of HMA was removed from the chase and excess paper and adhesive removed. The sample was then adjusted to ASTM conditions (temperature: 23 +/- 2 ° C., relative humidity: 50 +/- 5%) for 24 hours before testing. Tensile force was performed according to ASTM D-412. Tensile force dog bone was removed from the molded sheet and then tested in a tensile test apparatus with a gauge length of 1 inch and a crosshead speed of 12 inches / minute. Final tensile force was calculated as the mean value measured on four different dog bones.

In Table 1 below, the results presented for Examples 7 and 8 contribute to establishing an acceptable range for HMA performance as defined in the prior art. Example 7 shows that the very high molecular weight radial (SB) _n result is formulated at low rubber levels (11 wt.%), Which is H. B. Similar to the level outlined in US Pat. No. 5,037,411 to HB Fuller. Example 8 based on higher levels of rubber formulation (20% by weight) shows the results obtained for formulations similar to those described in US Pat. No. 4,526,577.

The results presented in Table (1) show that, as can be seen in Examples 1 and 2, the very high molecular weight linear SBS of the present invention is similar to that of the prior art examples described in Examples 7 and 8 of Table (1). It is shown to exhibit equivalent or better SAFT (shear adhesion failure temperature), seals, and HMA tensile forces. Additionally, it can be seen that in Examples 1 and 2 the adhesive viscosity is equal to or lower than prior art Examples 7 and 8 in Table (1). Lower viscosity facilitates application at lower temperatures.

It is also obvious that the results for Examples 4 and 6 could not be tolerated. Examples 4 and 6 each show very low SAFT and also have very low adhesive tension. These two SBS used are significantly lower than the molecular weight range defined by the present invention. This explains their poor performance. This low molecular weight SBS type will exhibit acceptable HMA performance in rubber formulations with higher amounts of rubber, with only 15 to 35% by weight, as shown in US Pat. No. 4,526,577.

In addition, it is obvious that Example 3 is inferior in performance as compared with Examples 1 and 2 in Table (1). The linear coupling SBS used in Example 3 has a sufficiently high molecular weight of 125,000 but also contains 21.3% by weight of residual unblocked double blocks. The remaining double block is due to low SAFT and HMA tensile force values. This demonstrates that the low double block SBS polymer produced by the continuous polymerization process leads to better results in the formulations of the present invention.

In high molecular weight linear SIS, the SAFT and HMA tensile performances of Examples 9, 10, 11, and 12 increase with increasing molecular weight, each of which is equivalent to or better than that of the prior art examples of Examples 7 and 8. Shows. Example 13 to obtain a high molecular weight linear coupling SIS illustrates the adverse effect of residual uncoupled double blocks.

The polymer of Example 14 is so low in molecular weight that it is insufficient in terms of performance (SAFT). This polymer has acceptable performance in formulations containing only more than 15% by weight of rubber.

The polymer of Example 15 has a sufficiently large molecular weight (MW), but due to its low styrene content and low polystyrene block molecular weight, this polymer has very low SAFT and HMA tensile forces.

TABLE 1

Low Rubber HMA Formulation

Example 1

To a 5 gallon stirred reactor under nitrogen atmosphere was added 12.3 kg of cyclohexane solvent and 106.3 g of 0.125M secondary butyl lithium in cyclohexane. The temperature of the reactor was brought to 76 ° C. and 301.4 g of styrene monomer was added. The styrene continued to polymerize for 36 minutes. The reaction mixture was cooled to 62 ° C. and 1406.4 g of butadiene monomer were added. Butadiene was polymerized for 45 minutes while the reaction temperature reached a maximum of 91.2 ° C. When 45 minutes passed, 301.4 g of styrene monomer was further added. After the reaction was continued for an additional 30 minutes, the reaction was terminated by adding excess isopropanol to the polymer solution. The polymer was recovered from the solution by addition of an antioxidant package consisting of hindered phenol and tris-nonylphenylphosphite (TNPP), followed by devolatilization at 100 ° C. for 3 hours in a vacuum oven under nitrogen. The resulting continuous polymerized linear SBS polymer had a styrene content of 31.1 wt% and a molecular weight (molecular weight adjusted for composition) was 124,700. SB double blocks (styrene butadiene double blocks) were not detected at all.

Example 2

This formulation was prepared according to the same general procedure as in Example 1 except that somewhat different weights of secondary butyl lithium, styrene and butadiene monomers were used. The resulting continuous polymerized linear SBS polymer had a styrene content of 31.0 wt% and a molecular weight (molecular weight adjusted for composition) was 117,770. SB double blocks were not detected at all.

Example 3

To a 5 gallon stirred reactor under nitrogen atmosphere was added 12.3 kg of cyclohexane solvent and 299.4 g of a 0.125M secondary butyl lithium solution in cyclohexane. The temperature of the reactor was brought to 75 ° C. and 589.7 g of styrene monomer were added. The styrene continued to polymerize for 45 minutes. The reaction mixture was cooled to 59 ° C. and 1409.4 g of butadiene monomer were added. Butadiene was polymerized for 65 minutes while the reaction temperature reached a maximum of 107 ° C. When 65 minutes had elapsed, the temperature was lowered to 50 ° C., and 43.3 g of 1.065 M dibromoethane coupling agent in cyclohexane was added to the reactor. After the coupling reaction was continued for 40 minutes, the reaction was terminated by adding excess isopropanol to the polymer solution. The polymer was recovered from the solution by addition of an antioxidant package consisting of hindered phenol and tris-nonylphenylphosphite (TNPP), followed by devolatilization at 100 ° C. for 3 hours in a vacuum oven under nitrogen. The resulting coupling linear SBS polymer had a styrene content of 31.1 wt% and a molecular weight (molecular weight adjusted for composition) was 124,700. The product also contained 21.3% by weight of residual SB double blocks that were uncoupled.

Examples 4 and 5

Examples 4 and 5 are continuous polymerized linear SBS polymers commercially available from DEXCO Polymers. Their properties are described in Table (1). These SBS polymers are representative types used in the formulations described in US Pat. No. 4,526,577.

Examples 6 and 8

Examples 6 and 8 are linear multiblock (tapered) SBS polymers available from Firestone. This product is the main example used in the formulations described in US Pat. No. 4,526,577. In Example 6, this polymer is formulated with 11 weight percent rubber, while in Example 8 the polymer is formulated with 20 weight percent rubber.

Example 7

Example 7 is a high molecular weight radial (SB) _n polymer of the type used in the formulations described in US Pat. No. 5,037,411.

Example 9

To a 5 gallon stirred reactor under nitrogen atmosphere was added 12.4 kg of cyclohexane solvent and 144.6 g of 0.125M secondary butyl lithium solution in cyclohexane. The temperature of the reactor was brought to 79 ° C. and 298.5 g of styrene monomer was added. The styrene continued to polymerize for 60 minutes. The reaction mixture was cooled to 61 ° C. and 1426.9 g of isoprene monomer were added. Isoprene was polymerized for 55 minutes while the reaction temperature reached a maximum of 98 ° C. When 55 minutes had elapsed, 298.5 g of styrene monomer was further added. After the reaction was continued for an additional 30 minutes, the reaction was terminated by adding excess isopropanol to the polymer solution. The polymer was recovered from the solution by addition of an antioxidant package consisting of hindered phenol and tris-nonylphenylphosphite (TNPP), followed by devolatilization at 100 ° C. for 3 hours in a vacuum oven under nitrogen. The resulting continuous polymerized linear SBS polymer had a styrene content of 30.8 wt% and a molecular weight (molecular weight adjusted for composition) was 120,000. No SI double block was detected.

Examples 10, 11, 12

Examples 10-12 were prepared according to the same general procedure as in Example 9 except that somewhat different weights of secondary butyl lithium, styrene and isoprene monomers were used. The resulting continuous polymerized linear SIS polymer had styrene content and molecular weight as described in Table (1).

Example 13

To a 5 gallon stirred reactor under nitrogen atmosphere was added 12.4 kg of cyclohexane solvent and 244.2 g of 0.125M secondary butyl lithium solution in cyclohexane. The temperature of the reactor was brought to 75 ° C. and 597.1 g of styrene monomer was added. The styrene was polymerized for 50 minutes. The reaction mixture was cooled to 59 ° C. and 1427.0 g of isoprene monomer were added. The isoprene was polymerized for 80 minutes while the reaction temperature reached a maximum of 92.8 ° C. When 80 minutes had elapsed, the temperature was lowered to 50 ° C., and 37.7 g of 1.065 M dibromoethane coupling agent in cyclohexane was added to the reactor. After the coupling reaction was continued for 40 minutes, the reaction was terminated by adding excess isopropanol to the polymer solution. The polymer was recovered from the solution by addition of an antioxidant package consisting of hindered phenol and tris-nonylphenylphosphite (TNPP), followed by devolatilization at 100 ° C. for 3 hours in a vacuum oven in a nitrogen atmosphere. The resulting coupling linear SBS polymer had a styrene content of 30.2 wt% and a molecular weight (molecular weight adjusted for composition) was 149,240. The product also contained 17.6% by weight of residual uncoupled SI double blocks.

Example 14

Example 14 is a continuous polymerized linear SIS polymer commercially available from Dexco Polymers. Their properties are described in Table (1). These SIS polymers are representative types used in the formulations described in US Pat. Nos. 5,143,968 and 5,149,741.

Example 15

Example 15 is a linear coupled SIS product commercially available from Shell Chemical.

Since a variety of different and different embodiments may be made within the scope of the invention set forth herein, and various modifications may be made in the embodiments herein detailed according to the requirements of patent law, the detailed description herein is intended to be limited. It is to be understood that the description is for purposes of illustration and not of purpose.

Claims (22)

A hot-melt adhesive composition suitable for disposable products, wherein the hot-melt adhesive composition can be used to bond one or more elastomeric, polyolefin, foam, polyethylene, polypropylene, or nonwoven layers to the substrate. Applied to polyolefin or nonwoven substrates by extrusion, spraying or multi-line technology; a) about 5 to about 15 weight percent of a linear ABA block copolymer based on the weight of the hot melt adhesive composition, wherein component B is polyisoprene, component A is polystyrene and is corrected for the composition of the polymer The average molecular weight of the polystyrene block is at least 18,000 and the total average molecular weight of the linear block copolymer, corrected for the composition of the polymer, is from about 120,000 to about 200,000, and component A is from about 25 to about 35 weight per 100 parts by weight of the block copolymer. Present in negative amounts); b) about 45 to about 85 weight percent of a compatible solid tackifying resin based on the weight of the hot melt adhesive composition; And c) A hot melt adhesive composition, optionally comprising from 0 to 35 weight percent of a plastic oil or liquid tackifying resin, based on the weight of the hot melt adhesive composition. The hot melt adhesive composition of claim 1, wherein the linear A-B-A block copolymer is from about 8 to about 13 weight percent based on the weight of the hot melt adhesive composition. The hot melt adhesive composition of claim 1, wherein the average molecular weight of the polystyrene block corrected for the composition of the polymer is from about 18,000 to about 22,000. The hot melt adhesive composition of claim 1, wherein the average molecular weight of the linear A-B-A block copolymer, corrected for the composition of the polymer, is from about 125,000 to about 150,000. The hot melt adhesive composition of claim 1, wherein component A is present in an amount of about 28 to about 32 parts by weight per 100 parts by weight of the A-B-A block copolymer. The hot melt adhesive composition of claim 1, wherein the A-B-A block copolymer contains less than 5% of residual A-B double blocks. The hot melt adhesive composition of claim 1, wherein the A-B-A block copolymer is produced in a coupling process with a coupling efficiency of greater than 95%. The hot melt adhesive composition of claim 1, wherein the A-B-A block copolymer is polymerized continuously to contain less than about 2% residual A-B double blocks. A hot melt adhesive composition suitable for a disposable article, wherein the hot melt adhesive composition is by extrusion, spraying or multi-line technology that can be used to bond one or more elastomeric, polyolefin, foam, polyethylene, polypropylene, or nonwoven layers to a substrate. Applied to a polyolefin or nonwoven substrate, a) about 5 to about 15 weight percent of a linear ABA block copolymer based on the weight of the hot melt adhesive composition, wherein component B is polybutadiene, component A is polystyrene and is corrected for the composition of the polymer The average molecular weight of the polystyrene block is at least 18,000 and the total average molecular weight of the linear block copolymer, corrected for the composition of the polymer, is from about 100,000 to about 180,000, and component A is from about 25 to about 35 weight per 100 parts by weight of the block copolymer. Present in negative amounts); b) about 45 to about 85 weight percent of a compatible solid tackifying resin based on the weight of the hot melt adhesive composition; And c) A hot melt adhesive composition, optionally comprising from 0 to 35 weight percent of a plastic oil or liquid tackifying resin, based on the weight of the hot melt adhesive composition. 10. The hot melt adhesive composition of claim 9, wherein the linear A-B-A block copolymer is about 8 to 13 weight percent based on the weight of the hot melt adhesive composition. 10. The hot melt adhesive composition of claim 9, wherein the average molecular weight of the polystyrene block corrected for the composition of the polymer is from about 18,000 to about 22,000. 10. The hot melt adhesive composition of claim 9, wherein the average molecular weight of the linear A-B-A block copolymer, corrected for the composition of the polymer, is from about 110,000 to about 140,000. 10. The hot melt adhesive composition of claim 9, wherein component A is present in an amount from about 28 to about 32 parts by weight per 100 parts by weight of the block copolymer. 10. The hot melt adhesive composition of claim 9, wherein the A-B-A block copolymer contains less than 5% of residual A-B double blocks. 10. The hot melt adhesive composition of claim 9, wherein the A-B-A block copolymer is produced in a coupling process with a coupling efficiency of greater than 95%. 10. The hot melt adhesive composition of claim 9, wherein the A-B-A block copolymer is continuously polymerized to contain less than about 2% residual A-B double blocks. a) about 5 to about 15 weight percent of a linear ABA block copolymer, wherein component A is polystyrene, based on the weight of the hot melt adhesive composition, in an amount of about 25 to about 35 weight parts per 100 weight parts of the block copolymer And the average molecular weight of the polystyrene block, corrected for the composition of the polymer, is at least 18,000, and the component B is i) polyisoprene, the total average molecular weight of the linear block copolymer, corrected for the composition of the polymer, of about 120,000. To about 200,000, or ii) polybutadiene, wherein the overall average molecular weight of the linear block copolymer, calibrated for the composition of the polymer, is from about 100,000 to about 180,000; b) about 45 to about 85 weight percent of a compatible solid tackifying resin based on the weight of the hot melt adhesive composition; And c) one or more tissues, nonwovens, polyethylene, polypropylene, elastomers, based on the weight of the hot melt adhesive composition, optionally with a hot melt adhesive composition comprising 0 to 35 weight percent of a plastic oil or liquid tackifying resin. A disposable article comprising at least one polyethylene or polypropylene substrate bonded to a polyolefin, or foam substrate. 18. The disposable article of claim 17 wherein the A-B-A block copolymer polymerizes continuously to contain less than about 2% residual A-B double blocks. 18. The disposable article of claim 17 wherein the A-B-A block copolymer contains less than 5% residual double blocks. 18. The disposable article of claim 17 wherein the A-B-A block copolymer is produced in a coupling process with a coupling efficiency of greater than 95%. The hot melt adhesive composition according to any one of claims 1 to 16, wherein the average molecular weight is an average peak molecular weight. The disposable article according to any one of claims 17 to 20, wherein the average molecular weight is an average peak molecular weight.