CN120310463A - Hot melt adhesives and their uses - Google Patents

Abstract

The present invention relates to a hot melt adhesive composition and its use, and in particular to a hot melt adhesive composition prepared from a mixture of propylene copolymers. The hot melt adhesive composition contains little or no oil, while providing high cohesion and excellent adhesion to nonwoven substrates and polymer films. The hot melt adhesive composition is particularly suitable for making absorbent structural articles.

Description

Hot melt adhesive and use thereof

Technical Field

The present invention relates to hot melt adhesive compositions prepared with mixtures of propylene copolymers. The hot melt adhesive composition contains little to no oil while providing high cohesion to the nonwoven substrate and polymer film and excellent adhesion. The hot melt adhesive composition is particularly suitable for the manufacture of absorbent structural articles.

Background

It is difficult to find a proper balance of flexibility and cohesiveness of the olefin-based hot melt adhesive. To achieve this balance, various polymer blends have been used to prepare hot melt adhesives, including blends of hydrogenated styrenic block copolymers and alpha-olefin copolymers in US2019/0382631A1, blends of thermoplastic styrenic block copolymers and propylene homopolymers in US 9822283B2, and blends of propylene/butene or propylene/hexene copolymers with polybutene-1 in US2020/0157385A 1.

Recent developments in olefin catalysts have provided more economical olefins, particularly polypropylene copolymers, in the marketplace. While propylene polymers have been candidates for hot melt adhesives, their rigidity and inability to adhere to substrates make them undesirable for use in hot melt adhesives. Adding rubber-based or amorphous ethylene copolymers to reduce the stiffness of propylene polymers, however, finding an appropriate balance of flexibility and cohesiveness for propylene-based hot melt adhesives has been challenging.

The hot melt adhesives described in US2017/0204306A1 and US2019/0144719A1 were prepared with semi-crystalline low molecular weight propylene having a DSC melting enthalpy of greater than 35J/g. While these adhesives are designed to improve creep retention of the bonded elastic film and elastic strands, they provide insufficient flexibility, as well as wet out and permeability to the film substrate at low coat weights.

The hot melt adhesive described in US2016/0102230A1 is prepared from a polypropylene impact copolymer having greater than 90 wt% propylene with a DSC melting point in the range of about 130 ℃ to about 165 ℃. However, softening points greater than 130 ℃ have high viscosities, and they require higher application temperatures and provide limited processability.

As described in US2017/0290945 A1, for hot melt adhesives prepared with propylene-based copolymers having a melt index of less than about 20 (measured at 190 ℃, 2.16 kg), a high oil content, i.e. greater than 20wt%, is required for adhesives of high viscosity and high application temperature.

There is a need in the art for propylene-based hot melt adhesives having an appropriate balance of flexibility and cohesiveness, and stable adhesive properties with minimal or no oil bleed and migration. The present invention meets this need.

Disclosure of Invention

The present invention provides hot melt adhesive compositions prepared from a mixture of propylene copolymers, which compositions are suitable for use in the manufacture of absorbent structural articles.

One aspect of the present invention is a hot melt adhesive comprising:

(a) About 20 to about 45 weight percent of a polymer mixture consisting of (1) and (2):

(1) A first polypropylene-polyethylene (co) polymer having (i) a viscosity of 3000cps to 8500cps at 190 ℃, (ii) a DSC melting heat value of less than about 5J/g measured according to ASTM D3418 at a heating rate of 10 ℃ per minute, (iii) a DSC melting peak at about 90-145 ℃ measured according to ASTM 3418 at a heating rate of 10 ℃ per minute, and

(2) A second polypropylene-polyethylene (co) polymer having (i) a melt index of from about 15 to about 40g/10min at 190 ℃ according to ASTM D1238, (ii) a DSC heat of fusion value of less than about 15J/g measured at 10 ℃ heating rate according to ASTM D3418;

wherein the mass ratio of the first polypropylene-polyethylene (co) polymer to the second polypropylene-polyethylene (co) polymer is from about 3:1 to about 6.5:1;

(b) About 30wt% to about 60wt% of a tackifier

The hot melt adhesive has (i) a tan (delta) value of greater than about 30 at 140 ℃,10 rad/s and (ii) a melt viscosity of from about 1,500cps to about 11,000cps at 150 ℃ as measured according to ASTM 3236. The hot melt adhesive optionally has up to about 30wt% of a wax or polyolefin liquid plasticizer;

in another aspect, the present invention relates to a hot melt adhesive consisting essentially of:

(a) About 20 to about 45 weight percent of a polymer matrix prepared from a mixture of (1) and (2):

(1) A first polymer system, wherein the first polymer system has (i) a viscosity of 3000 to 8500cps at 190 ℃, (ii) a DSC melting heating value of less than about 5J/g measured according to ASTM D3418 at a heating rate of 10 ℃ per minute, (iii) a DSC melting peak measured according to ASTM 3418 at a heating rate of 10 ℃ per minute of about 90 to 145 ℃, and (iv) propylene and ethylene (co) monomer, and

(2) A second polymer system, wherein the second polymer system has (i) a melt index of from about 15 to about 40g/10min at 190 ℃ according to ASTM D1238, (ii) a DSC heat of fusion value of less than about 15J/g measured at 10 ℃ heating rate according to ASTM D3418, and (iii) propylene and ethylene (co) monomers;

Wherein the mass ratio of the first polymer system to the second polymer system is from about 3:1 to about 6.5:1;

(b) About 30 to about 60 weight percent of a tackifier.

(C) About 10 to about 30 weight percent of a wax or polyolefin liquid plasticizer, and

(D) From about 0.1 to about 6wt% of an additive selected from the group consisting of fillers, antioxidants, colorants, fillers, pigments, UV absorbers, UV inhibitors, compatible coatings for packaging purposes.

The hot melt adhesive has (i) a tan (delta) value of greater than about 30 at 140 ℃ at 10rad/s and (ii) a melt viscosity of from about 1,500cps to about 11,000cps at 150 ℃ as measured according to ASTM 3236.

Detailed Description

"Absorbent article" refers to devices that absorb and contain body exudates, and, more specifically, refers to devices that are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Exemplary absorbent articles include diapers, training pants, pull-on pant-type diapers (i.e., diapers having preformed waist and leg openings as shown in U.S. Pat. No. 6,120,487), refastenable diapers or pant-type diapers, incontinence pads (incontinence briefs) and undergarments, diaper holders and liners, feminine hygiene garments such as panty liners, absorbent inserts, meat pads, animal pads, face masks, coveralls, and the like.

By "absorbent structural adhesive" is meant an adhesive that binds components of an absorbent article (including absorbent pads, nonwoven, topsheets, backsheets, core wraps, core stabilizers, and core fasteners) together.

"Adhesively bonded" to a substrate, wherein the adhesive is used to bond the substrate (e.g., film, polymer film, elastic film, nonwoven, and tissue) or to a second similar or different substrate.

As used herein, "comprising," "including," "having," "can," "containing," and variations thereof are open-ended terms that each specify the presence of the stated features (e.g., components), but do not preclude the presence of other features (e.g., elements, steps, components, etc., known in the art, or disclosed herein). However, such description should be construed as also describing the composition or method as "consisting of the recited ingredients/steps" which allows for the presence of only the given ingredients/steps and any impurities that may result therefrom, and excludes other ingredients/steps.

"Consisting essentially of" is used herein to limit the scope of the subject matter (e.g., the scope of the subject matter in the claims) to the materials or steps specified, as well as those materials or steps that do not materially affect the basic and novel characteristics of the subject matter.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

The numerical values in the specification and claims of this application, particularly as they relate to polymers or polymer compositions, reflect average values for compositions that may contain individual polymers of different characteristics. Furthermore, unless indicated to the contrary, the numerical values should be understood to include the same numerical values when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

All ranges disclosed herein are inclusive of the endpoints and independently combinable (e.g., the range of "2 to 10" is inclusive of endpoints 2 and 10, and all intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and are sufficiently imprecise to include values near these ranges and/or values. As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Thus, in some cases, a value modified by one or more terms such as "about" may not be limited to the precise value specified. In at least some cases, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "about 2 to about 4" also discloses a range of "2 to 4". The term "about" may refer to plus or minus 10% of the indicated number. For example, "about 10%" may mean a range of 9% to 11%, and "about 1" may mean 0.9-1.1. Other meanings of "about" may be apparent from the context, such as rounding, so that, for example, "about 1" may also mean 0.5 to 1.4.

The present invention provides sprayable hot melt adhesives that can be applied at 160 ℃ or less. The sprayable hot melt adhesive has high initial strength (GREEN STRENGTH) and excellent adhesive strength. The sprayable hot melt adhesive can be applied as a thin glue line without the risk of oozing out and burn-through of the heat sensitive substrate.

One aspect of the present invention is a hot melt adhesive comprising from about 20 to about 45 weight percent of a polymer mixture and from 30 to about 60 weight percent of a tackifier. The hot melt adhesive optionally comprises up to about 30wt% of a wax or polyolefin liquid plasticizer.

The polymer mixture consists of:

(1) A first polypropylene-polyethylene (co) polymer having (i) a viscosity of 3000cps to 8500cps at 190 ℃ according to ASTM D3236, (ii) a DSC melting heat value of less than about 5J/g measured at a heating rate of 10 ℃ per minute according to ASTM D3418, (iii) a DSC melting peak at about 90-145 ℃ measured at a heating rate of 10 ℃ per minute according to ASTM 3418, and

(2) A second polypropylene-polyethylene (co) polymer having (i) a melt index of from about 15 to about 40g/10min at 190 ℃ according to ASTM D1238, (ii) a DSC heat of fusion value of less than about 15J/g measured at 10 ℃ heating rate according to ASTM D3418;

Further, the mass ratio of the first polypropylene-polyethylene (co) polymer to the second polypropylene-polyethylene (co) polymer is from about 3:1 to about 6.5:1. Surprisingly, the combination of two polypropylene-polyethylene (co) polymers provides flexibility and adhesion in the adhesive even without the addition of rubber or amorphous polymers.

In another embodiment, the hot melt adhesive consists essentially of about 20 to about 45 weight percent of the polymer system, about 30 to about 60 weight percent of the tackifier, about 10 to about 30 weight percent of the wax or plasticizer, and about 0.1 to about 6 weight percent of an additive selected from the group consisting of fillers, antioxidants, colorants, UV absorbers, UV inhibitors, pigments, compatible coatings for packaging purposes, and the like.

The polymer system is a mixture of (1) a first polymer system and (2) a second polymer system, wherein the first polymer system has (i) a viscosity of about 3,000 to about 8500cps, preferably about 5,000 to about 8,500, at 190 ℃, (ii) a DSC melting heat value of less than about 5J/g, measured at 10 ℃ per minute heating rate, according to ASTM D3418, (iii) a DSC melting peak of about 90-145 ℃ measured at 10 ℃ per minute heating rate, according to ASTM 3418, and (iv) propylene and ethylene (co) monomer, wherein the second polymer system has (i) a melt index of about 15 to about 40g/10min, measured at 10 ℃ per minute heating rate, according to ASTM D1238, and (iii) a DSC melting heat value of less than about 15J/g, measured at 10 ℃ per minute heating rate, according to ASTM D3418, and (iii) propylene and ethylene (co) monomer. The mass ratio of the first polymer system to the second polymer system is from about 3:1 to about 6.5:1.

It has been found that hot melt adhesives prepared with two specific polypropylene (co) polymers (at specific ratios of about 3:1 to about 6.5:1) provide flexibility for good initial strength and adequate open time. This is achieved without additional rubber or amorphous polymers and without paraffin and naphthene oils.

In one embodiment, the two polypropylene (co) polymers are amorphous in nature. The heat of fusion is directly related to the crystallinity of the polymer. For polypropylene (co) polymers of sprayable hot melt adhesives, a low level of crystallinity is desirable.

A suitable first polypropylene-polyethylene (co) polymer is an amorphous poly-alpha-olefin (APAO) prepared by polymerization with a Ziegler-Natta catalyst. Suitable amorphous poly-alpha-olefin polymers are random copolymers of propylene and ethylene monomers, including Aerafin from Synthomer, DREX RT 2935 and DREX RT 2975 from REXtac LLC. Another suitable first polypropylene-polyethylene (co) polymer is an amorphous polypropylene copolymer prepared by polymerization with a metallocene catalyst. Suitable second polypropylene-polyethylene (co) polymers include, inter alia, vistamaxx 6502 from ExxonMobil Chemical. The polymer blend having a specific viscosity/melt flow index of the first and second polypropylene-polyethylene (co) polymers provides a suitable balance of flexibility and cohesion for the hot melt adhesive.

Useful tackifying resins can include any compatible resin or mixtures thereof such as aliphatic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins and hydrogenated derivatives thereof, and cycloaliphatic petroleum hydrocarbon resins and hydrogenated derivatives thereof. Examples of particularly suitable hydrogenated petroleum hydrocarbon tackifiers include Escorez 5400 and 5300 from Exxon Mobil Chemicals, arkon P115 from Arakawa, eastotac 100R,100W,Regalite S1100 and R1100 from EASTMAN CHEMICAL, LUHOREZ HD 1100 from Tianjin Luhua Chemical Co.Ltd, SUKOREZ SU-100 and SU-500 from Kolon Industries, HC-100 and HS-100 from Hanwha Solutions Corp, HM1000 from HENGHE MATERIALS & Science Technology Co.Ltd, HM1000 from Ningbo Jinhai Chenguang Chemical Corp, HAITACK JH 6100, and the like. Also included are cyclic or acyclic C ₅ resins and aromatic modified acyclic or cyclic resins. Examples of commercially available C ₅ resins include Wingtack 98,Wingtack extra,Wingtack ET from CRAY VALLEY USA LLC, piccotac 9095 and 1095 from EASTMAN CHEMICAL, escorez 2203LC from Exxon Mobil Chemicals, luhorez A from Luhua Chemical Corp, a2100, quintone R and C210 from Zeon Chemicals co.ltd, and S195. Also included are polyterpene resins, phenolic modified terpene resins and hydrogenated derivatives thereof, including, for example, resin products resulting from the condensation of a bicyclic terpene and phenol in an acidic medium. Examples of commercially available modified terpene resins are SYLVARES TR M and TR 126 from Kraton Chemical b.v. Sylvares6100, NG98, TP 2040HM and SYLVARES TP, both available from Kraton Chemical b.v. Kraton Chemical b.v. Examples of commercially available rosins and rosin derivatives useful in the practice of the invention include SYLVALITE RE L and SYLVARES RE 115 available from Kraton Chemical b.v., hydrogenated rosins and rosin derivatives such as Foral 105 from Pinova Incorporated. Other useful tackifying resins include natural and modified rosins including, for example, gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, resin acid esters, and polymerized rosin, glycerol and pentaerythritol esters of natural and modified rosins including, for example, glycerol esters of pale wood rosin, glycerol esters of hydrogenated rosin, glycerol esters of polymerized rosin, pentaerythritol esters of hydrogenated rosin, and phenol-modified pentaerythritol esters of rosin, copolymers and terpolymers of natural terpenes including, for example, styrene/terpene and alpha-methylstyrene/terpene.

Preferred tackifiers include C ₅ resins, petroleum distillates, hydrogenated hydrocarbons, C ₅/C₉ resins, C ₉ resins, polyterpenes, rosins, hydrogenated rosins, rosin esters, and mixtures thereof.

Also useful are aromatic hydrocarbon resins derived from C ₉ aromatic/aliphatic olefins and available under the trade name Norsolene from Sartomer and CRAY VALLEY, and the series of TK aromatic hydrocarbon resins available from Rutgers. Norsolene 1100 is a low molecular weight thermoplastic hydrocarbon polymer commercially available from CRAY VALLEY.

Alpha-methylstyrene such as Kristalex F115,1120 and 5140 from EASTMAN CHEMICALS, SYLVARES SA series from Arizona chemicals, can also be used as tackifiers in the present invention. Some formulations may require a mixture of two or more of the tackifying resins.

Suitable waxes include paraffin waxes, microcrystalline waxes, polyethylene waxes, polypropylene waxes, by-product polyethylene waxes, fischer-Tropsch waxes, oxidized Fischer-Tropsch waxes and functionalized waxes (e.g., hydroxystearamide waxes and fatty amide waxes). High density low molecular weight polyethylene waxes, by-product polyethylene waxes and Fischer-Tropsch waxes are commonly referred to in the art as synthetic high melting point waxes. Useful waxes include polyethylene and polypropylene waxes available in the LICOCENE series, such as LICOCENE PE 4201, PE3101 from Clariant Corp, LICOWAX PE 520 and LOCTAS PE PE310 from Clariant Corp, salsolwax H from SASOL Chemicals, seration 1820 from SASOL Chemicals and the AC series such as AC-9, AC-8, AC-820A and L-C101N from Lion Chemtech Co.Ltd.

The hot melt adhesive of the present invention is substantially free of any paraffinic or naphthenic oils at room temperature. "substantially free" or "free" is defined herein to include unavoidable levels of impurities, but not to include further impurities. Non-oil polyolefin liquid plasticizers are suitable as plasticizers in hot melt adhesives. Suitable polyolefin liquid plasticizers include polypropylene, polybutene, polyisobutene, and the like. Examples of commercially available non-oil polyolefin plasticizers are Indopol H100, H300, H900, H1500 from INEOS Oligomers, PB 950 from Daelim Industrial Co Ltd, TPC 1105, TPC 1160 from group TPC (Texas Petrochemicals), PIB 32, PIB 24 from Braskem S.A, licocene PPA 330 from Clariant.

The sprayable low application temperature hot melt adhesives of the invention may also desirably contain at least one stabilizer and/or at least one antioxidant. These compounds are added to protect the adhesive from degradation due to reaction with oxygen induced by, for example, heat, light or residual catalyst from the raw materials such as tackifying resins.

Useful stabilizers or antioxidants included herein are 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 phenolic compounds that also contain sterically bulky radicals in the vicinity of the phenolic hydroxyl group thereof. In particular, tertiary butyl groups are typically substituted on the benzene ring in at least one ortho position relative to the phenolic hydroxyl group. These sterically bulky substituted radicals are present in the vicinity of the hydroxyl group and delay its stretching frequency and correspondingly its reactivity, and thus this hindrance provides the phenolic compound with its stabilizing properties. Representative hindered phenols include 1,3, 5-trimethyl-2, 4, 6-tris- (3, 5-di-tert-butyl-4-hydroxybenzyl) -benzene, pentaerythritol tetra-3 (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionate, n-octadecyl-3 (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionate, 4 '-methylenebis (2, 6-tert-butylphenol), 4' -thiobis (6-tert-butylo-cresol), 2, 6-di-tert-butylphenol, 6- (4-hydroxyphenoxy) -2, 4-bis (n-octylthio) -1,3, 5-triazine, di-n-octylthio ethyl 3, 5-di-tert-butyl-4-hydroxy-benzoate, and sorbitol hexa [3- (3, 5-di-tert-butyl-4-hydroxy-phenyl) -propionate ].

These antioxidants are commercially available from BASF and include565,1010,1076 And 1726, which are hindered phenols. These are primary antioxidants acting as radical scavengers and can be used alone or in combination with other antioxidants such as phosphite antioxidants (e.g., available from BASF168, EVERFOS from EVERSPRING CHEMICAL Company). Phosphite antioxidants are considered secondary antioxidants and are not generally used alone. These are mainly used as peroxide decomposers. Other available antioxidants are those available from SolvayLTDP and commercially available from HM Royal330, Evernox from EVERSPRING CHEMICAL Company and BNX 1010 from Mayzo. Many such antioxidants may be used alone or in combination with other such antioxidants. These compounds are added in small amounts to the hot melt, typically less than about 10wt%, and have no effect on other physical properties. Other compounds that may be added that also do not affect the physical properties are pigments that add color, or fluorescers, to mention just a few. These additives are known to those skilled in the art.

Other additives commonly used in hot melt adhesives to meet different properties and to meet the requirements of a particular application may also be added to the adhesive composition of the present invention. Such additives include, for example, fillers, pigments, flow modifiers, dyes, ionic and nonionic surfactants, compatible coatings for packaging purposes that prevent the adhesive from sticking together, which may be incorporated into the adhesive formulation in small or greater amounts depending on the purpose.

The hot melt adhesive composition is prepared by melt blending the components at a temperature of about 150 ℃ to about 180 ℃ to form a homogeneous blend, typically for about two hours. Various blending methods are known in the art, and any method that produces a homogeneous blend may be used. The blend is then cooled and may be formed into pellets, small pieces, mini-pieces, or pieces for storage or shipment as a preformed adhesive. These preformed adhesives may then be reheated and melted for application to a substrate.

The resulting hot melt adhesive has (i) a tan (delta) value of greater than about 30 at 140 ℃ at 10rad/s and (ii) a melt viscosity of from about 1,500 to about 11,000cps at 150 ℃ as measured according to ASTM 3236.

The hot melt adhesive compositions are suitable for joining absorbent structural articles, particularly sanitary absorbent structural articles, including diapers, diaper pants, baby wipes, training pants, absorbent underpants, child care pants, swim wear and other disposable garments, feminine care products including sanitary napkins, wet wipes, menstrual pads, panty liners, panty shields, tampons and tampon applicators, adult care products including wet wipes, liners, containers, incontinence products and urine covers, garment components, sports and recreational products, products for thermal or cold therapy, medical gowns (i.e., protective and/or surgical gowns), surgical drapes (surgical drapes), hats, gloves, masks, bandages, wound dressings, wet wipes, covers, containers, filters, disposable garments and mattresses, medical absorbent garments, pads, building and packaging, industrial pads (including meat pads), products for cleaning and sanitizing, wet wipes, covers, filters, towels, toilet paper, facial tissues, nonwoven webs, home comfort products including pillows, pads, back pads, masks, and body care products such as products for cleaning or treating skin, laboratory wear, coveralls, and, etc. Sprayable low application temperature adhesives may also be used for bottle labeling or other applications involving plastic bonding or removable pressure sensitive adhesive applications.

It will be apparent to those skilled in the art that many modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Examples

The invention will be further described in the following examples, which are included for the purpose of illustration and are not intended to limit the scope of the invention in any way.

The heat of fusion (ΔH) and the melting temperature Tm of the polymer were measured by DSC (differential scanning calorimeter, TAI model Q1000 DSC) according to ASTM D3418 at a rate of 10℃per minute for both heating and cooling cycles.

The viscosities of the adhesives and polymers were measured according to ASTM 3236 using a standard Brookfield viscometer at 140 ℃,150 ℃,160 ℃ and 190 ℃ with a rotor 27.

Tan delta was obtained using a TA dynamic mechanical Analyzer (DYNAMIC MECHANICAL Analyzer) (ARes-MLS) using a temperature ramp test from Orchestrators software version 7.2.0.4. The test uses parallel steel plates (316 stainless steel, part #708-00966-1 from TA instruments) 25mm in diameter and separated by a gap of about 1 mm. The sample is loaded and then heated to 160 ℃ at the desired temperature, and once equilibrium 160 ℃ is reached, the temperature ramp begins. The program measures data every 10 seconds. The convection oven (ARES-LN 2 type) was continuously purged with cold nitrogen. The cooling rate was 5 ℃/min until 0 ℃ was reached. The convection oven was continuously purged with nitrogen. The frequency is kept at 10rad/s. The initial strain at the start of the test was 50% (at the outer edge of the plate). The automatic strain option in the software is used to maintain an accurately measurable torque throughout the test. This option is configured such that the maximum application strain allowed by the software is 80%. The automatic strain program adjusts the strain at each temperature increment, if necessary. If the torque is below 19.62 x 10 ^-3 Nm, the strain is reduced by 5% of the current value. If the torque exceeds 117.72 x 10 ^-3 Nm, the torque is reduced by 25% of the current value. At a torque of 19.62×10 ^-3 to 117.72 ×10 ^-3 Nm, no strain change was produced at this temperature increase. The shear storage modulus or elastic modulus (G') and shear loss modulus (G ") are calculated by software from the torque and strain data. tan delta is reported as G "/G' at 140 ℃, i.e

Tan δ=g "/G' (at 140 ℃).

The polypropylene copolymers in the adhesive samples are summarized in table 1.

TABLE 1 Polypropylene (Co) Polymer description

*Exxon Mobile

**Synthomer

***REXtac LLC

****Evonik Industries

A measured at 190 ℃ per 2.16kg, ASTM D1238

B measured at 190 ℃, ASTM 3236

C determination by DSC according to ASTM D3418

Adhesive samples are shown in table 2 as adhesive examples D1, E1, J, L and M. The adhesive is formulated with various polypropylene polymers with tackifiers, waxes, plasticizers, and antioxidants. HM-1000 is a hydrogenated hydrocarbon tackifier from HENGHE MATERIAL & Science Technology Co., ltd.; licocene PE4201 is a polyethylene wax from Clariant; licocene PPA 330 is a polyolefin liquid plasticizer from Clariant; evernox 10 is an antioxidant from EVERSPRING CHEMICAL Company.

TABLE 2 adhesive examples

For each adhesive sample, the components were heated and mixed at 160 ℃ until uniform. An adhesive is then applied between the two substrates to form an adhesive article. Two different adhesive articles were prepared. The first bonded article (nonwoven-film) was formed by bonding a breathable polyester (poly) BR149 from the Clopay substrate and a 15gsm nonwoven from the PGI substrate to the adhesive sample. The second adhesive article (film-film) was formed by adhering an air impermeable polyethylene film having a thickness of 0.65mil to another air impermeable polyethylene film with an adhesive sample. The adhesive was applied to the substrate using a signature applicator (Signature Spray applicator head) from Nordson Corp at a line speed of 1000 feet per minute at 150-155C, with a coat weight of 2.5gsm or 4gsm. The initial adhesive strength results for the corresponding adhesive samples are shown in table 3.

The initial adhesive strength of the samples was determined as:

adhesive strength [ g/in ] = average peel force [ g ]/sample width [ in ].

The average adhesive strength was determined using a minimum of 5 samples.

The bond strength between the nonwoven and film and between the film and film was measured on the samples using a tensile tester in a mode I T-peel configuration in a Sintech 1/D tensile tester (TENSILE TESTING MACHINE) (MTS, model 1500BZF-50, USA). The stretcher was equipped with a high precision 300lb load cell. The test samples had a substantially rectilinear shape with a precision cutter from Thwing-Albert Instruments co., philiadelphia, PA. The sample size is selected to achieve the desired strain with a force suitable for the instrument. The sample dimensions were about 2 inches wide by about 6 inches long. The length of the sample was aligned with the machine direction (MD direction). The samples were equilibrated at 23 ± 2 ℃ for at least one hour and then tested at the same temperature. The holder and clamp are fitted with lightweight jaws (either flat or bar-shaped wires can be used) that are sized to fit the sample size being tested. The instrument was calibrated according to the manufacturer's instructions. The distance between the clamping force lines (gauge length) is 1 inch, which is measured with a steel ruler clamped beside the clamp. The force readings on the instrument are zeroed to account for the mass of the holder and clamp. Samples (2 inches wide by about 6 inches long) were prepared for the T-peel test using the following procedure. The laminate samples were separated about 1 inch on top and the polyester side and nonwoven side were taped. The samples were mounted in a T-peel configuration into the clamps with the film portion of the T-peel samples mounted in the bottom clamp and the nonwoven portion of the T-peel samples mounted in the top clamp. The sample was mounted in the fixture with minimal slack. The crosshead was moved upward at a constant crosshead speed of 12in/min and the sample was peeled off until the materials (nonwoven fibers and films) were completely separated. Force and elongation data obtained at a rate of 50Hz during peeling were measured. The peel force (gf) during the first 8 inch extension is reported as Mode I (Mode I) bond strength. The average initial adhesive strength was determined using a minimum of 5 samples.

The preferred initial peel strength of the adhesive is equal to or greater than 150gf/inch on the particular substrate. Typically, articles formed with adhesives having greater than 150gf/inch provide substrate deformation and tear, which indicates failure at the substrate rather than failure of an adhesive bond.

TABLE 3 adhesive Properties

* Substrate breathable polyester BR149 (from Clopay) bonded to 15gsm nonwoven (from PGI)

* Substrate a non-breathable polyethylene film having a thickness of 0.65mil was bonded to a second non-breathable polyethylene film having a thickness of 0.65mil

Adhesive samples J, L and M provided an initial adhesive strength of greater than 150 gf/inch. These adhesive samples were made with a first polypropylene-polyethylene (co) polymer having (i) a viscosity of 3,000cps to 8500cps at 190 ℃, (ii) a DSC melting heat value of less than about 5J/g measured at 10 ℃ per minute heating rate according to ASTM D3418, and (iii) a DSC melting peak of about 90 ℃ to 145 ℃ measured at 10 ℃ per minute heating rate according to ASTM 3418.

Adhesive samples D1 and E1 were prepared with polymers outside of the desired viscosity and/or melting temperature. They are very viscous, provide poor adhesion patterns, or cannot be sprayed at temperatures below 160 ℃.

Claims (15)

1. A hot melt adhesive comprising: (a) from about 20 wt% to about 45 wt% of a polymer mixture consisting of (1) and (2): (1) a first polypropylene-polyethylene (co)polymer having (i) a viscosity of 3000 cps to 8500 cps at 190°C, (ii) a DSC heat of fusion value of less than about 5 J/g measured at a heating rate of 10°C/min according to ASTM D3418, (iii) a DSC melting peak at about 90-145°C measured at a heating rate of 10°C/min according to ASTM 3418; and (2) a second polypropylene-polyethylene (co)polymer having (i) a melt index of about 15 to about 40 g/10 min at 2.16 kg and 190° C. according to ASTM D1238, and (ii) a DSC heat of fusion value of less than about 15 J/g at a heating rate of 10° C./min as measured according to ASTM D3418; wherein the mass ratio of the first polypropylene-polyethylene (co)polymer to the second polypropylene-polyethylene (co)polymer is from about 3:1 to about 6.5:1; (b) from about 30 wt % to about 60 wt % of a tackifier; and (c) optionally up to about 30 wt % of a wax or plasticizer; The hot melt adhesive has (i) a tan (δ) value of greater than about 30 at 140° C., 10 rad/s and (ii) a melt viscosity of about 1,500 cps to about 11,000 cps at 150° C. as measured according to ASTM 3236. 2. The hot melt adhesive of claim 1, wherein the first polypropylene-polyethylene (co)polymer is prepared using a metallocene catalyst. 3. The hot melt adhesive of claim 1, wherein the first polypropylene-polyethylene (co)polymer is prepared using a Ziegler-Natta catalyst. 4. The hot melt adhesive according to any one of claims 1 to 3, wherein the first polypropylene-polyethylene (co)polymer has a viscosity of 5000 cps to 8500 cps at 190°C. 5. The hot melt adhesive according to any one of claims 1 to 4, wherein the second polypropylene-polyethylene (co)polymer has a melt index of about 15 to about 40 g/10 min at 2.16 kg and 190°C. 6. The hot melt adhesive of any one of claims 1 to 5, wherein the tackifier is selected from the group consisting of _C5 resins, petroleum distillates, hydrogenated hydrocarbons, _C5 / _C9 resins, _C9 resins, polyterpenes, rosin, hydrogenated rosin, rosin esters, and mixtures thereof. 7. The hot melt adhesive of any one of claims 1 to 6, wherein the wax is selected from polyethylene wax and polypropylene wax. 8. The hot melt adhesive according to any one of claims 1 to 7, wherein the plasticizer is a non-oil polyolefin liquid plasticizer selected from polybutene, polyisobutylene, polypropylene or a mixture thereof. 9. The hot melt adhesive according to any one of claims 1 to 8, wherein the hot melt adhesive is substantially free of oil. 10. The hot melt adhesive according to any one of claims 1 to 9, further comprising an additive selected from antioxidants, colorants, fillers, UV absorbers, UV inhibitors, pigments, compatible coatings for packaging purposes and mixtures thereof. 11. A hot melt adhesive consisting essentially of: (a) from about 20 to about 45 wt % of a polymer matrix prepared from a mixture of (1) and (2): (1) a first polymer system, wherein the first polymer system has (i) a viscosity of 3000-8500 cps at 190°C, (ii) a DSC heat of fusion value of less than about 5 J/g measured at a heating rate of 10°C/min according to ASTM D3418, (iii) a DSC melting peak at about 90-145°C measured at a heating rate of 10°C/min according to ASTM 3418, and (iv) propylene and ethylene (co)monomers; and (2) a second polymer system, wherein the second polymer system has (i) a melt index of about 15 to about 40 g/10 min at 2.16 kg and 190° C. according to ASTM D 1238, (ii) a DSC heat of fusion value of less than about 15 J/g at a heating rate of 10° C./min measured according to ASTM D3418, and (iii) propylene and ethylene (co)monomers; wherein the mass ratio of the first polymer system to the second polymer system is from about 3:1 to about 6.5:1; (b) about 30 to about 60 weight percent of a tackifier; (c) from about 10 to about 30 wt % of a wax or plasticizer; and (d) from about 0.1 to about 6 weight percent of an additive selected from the group consisting of antioxidants, colorants, fillers, UV absorbers, UV inhibitors, pigments, compatible coatings for packaging purposes, and mixtures thereof; The hot melt adhesive has (i) a tan (δ) value of greater than about 30 at 140° C., 10 rad/s and (ii) a melt viscosity of about 1,500 to about 11,000 cps at 150° C. as measured according to ASTM 3236. 12. An article comprising the adhesive of any one of claims 1 to 11. 13. The article of claim 12, wherein the adhesive is disposed between two substrates. 14. The article according to claim 13, wherein the substrate is selected from the group consisting of nonwoven fabrics, polymer films, elastic films and tissues. 15. The article of any one of claims 12 to 14, which is a diaper, training pants, absorbent underwear, swimwear, sanitary napkin, tampon, disinfecting wipes, facial wipes, medical gowns, meat pads, face masks, coveralls, surgical drapes, caps, gloves, face masks, bandages, wound dressings, filters, mattresses, panty liners, towels, toilet paper, facial tissue, or animal pads.