Patent Description:
Hot melt adhesives containing a thermoplastic block copolymer as a main component have been widely used in disposable products such as a diaper and a napkin and are applied to a base material, for example, a nonwoven fabric, a tissue, a polyethylene (PE) film and the like (see e.g. <CIT>).

Typical thermoplastic block copolymers used in the traditional hot melt adhesives are styrenebutadiene-styrene (SBS) block copolymers and styrene-isoprene-styrene (SIS) block copolymers.

The traditional hot melt adhesives, however, usually have high melt viscosity. If used at a higher temperature, the hot melt adhesives are likely to burn the PE films or other substrates to be applied on. If used at a lower temperature, the hot melt adhesives often cannot be coated onto the substrates properly.

In addition, it has been shown that together with elastic films, ink, and super adsorbent polymers (SAP), hot melt adhesive is one of the major sources of odor for disposable products. Not only hot melt adhesive itself emits odor when being heated to the application temperature, it also heats up the substrate in contact with the hot melt adhesive which could further release odorous molecules.

Therefore, there is a need for developing a hot melt adhesive that can be applied at low temperature, has excellent T peel strength and low odor after being applied in the disposable products.

The present invention relates to a hot melt adhesive composition as defined in claim <NUM>.

The hot melt adhesive composition of the invention has a small melt viscosity and can be applied at a low temperature range of <NUM> to <NUM>. The hot melt adhesive composition also has excellent T peel strength and low odor after being applied in the disposable products.

The present invention also relates to an article comprising a substrate bonded to the hot melt adhesive composition as defined in the claims, the substrate is selected from the group consisting of a woven fabric, a nonwoven fabric, a rubber, a resin, tissues, polyolefin films, elastic films and elastic strands.

In the following passages the present invention is described in more detail. Each aspect so described may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In the context of the present invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or process steps.

All references cited in the present specification are hereby incorporated by reference in their entirety.

In the context of this disclosure, a number of terms shall be utilized.

The term "hydrogenated thermoplastic block copolymer" according to the invention means a copolymer of a vinyl-based aromatic hydrocarbon with a conjugated diene, which is fully or partially hydrogenated.

The term "vinyl-based aromatic hydrocarbon" means an aromatic hydrocarbon compound having a vinyl group, and specific examples thereof include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, <NUM>,<NUM>-dimethylstyrene, a-methylstyrene, vinylnaphthalene, vinylanthracene and the like. The vinyl-based aromatic hydrocarbons can be used alone, or in combination.

The term "conjugated diene" means a diolefin compound having at least a pair of conjugated double bonds, and specific examples thereof include <NUM> ,<NUM>-butadiene, <NUM>-methyl-<NUM> ,<NUM>-butadiene (or isoprene), <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-pentadiene, <NUM>,<NUM>-hexadiene and the like. The conjugated diene can be used alone, or in combination.

The hydrogenated thermoplastic block copolymer of the present invention refers to at least one hydrogenated thermoplastic block copolymer with a melt index greater than or equal to <NUM>/<NUM> as determined according to ASTM D-<NUM> at <NUM>/<NUM>, wherein the hydrogenated thermoplastic block copolymer is a copolymer of a vinyl-based aromatic hydrocarbon with a conjugated diene. The melt index may be greater than or equal to <NUM>/<NUM>, such as greater than or equal to <NUM>/<NUM>, greater than or equal to <NUM>/<NUM>, greater than or equal to <NUM>/<NUM>, or greater than or equal to <NUM>/<NUM>, determined according to ASTM D-<NUM> (<NUM>, <NUM> load).

In some embodiments of the present inventions, the hydrogenated thermoplastic block copolymer may have a melt index less than or equal to <NUM>/<NUM>, such as less than or equal to <NUM>/<NUM>, less than or equal to <NUM>/<NUM>, less than or equal to <NUM>/<NUM>, or less than or equal to <NUM>/10mins, determined according to ASTM D-<NUM> (<NUM>, <NUM> load).

The hydrogenated thermoplastic block copolymer includes but not limited to styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-ethylene-propylene-styrene (SEPS) block copolymer, styrene-ethylene-ethylene/propylene-styrene (SEEP) block copolymer and any combination thereof.

Commercially available hydrogenated thermoplastic block copolymer is, for example, MD <NUM> from Kraton.

The polyolefin of the present invention refers to at least one polyolefin with a melt viscosity less than or equal to <NUM> mPa·s (<NUM> cPs) at <NUM>, wherein said at least one polyolefin is selected from polyethylene, polypropylene, polybutene, and the copolymers and terpolymers thereof. The melt viscosity may be less than or equal to <NUM> cPs at <NUM>, less than or equal to <NUM> cPs at <NUM>, less than or equal to <NUM> cPs at <NUM> or less than or equal to <NUM> cPs at <NUM>.

In some embodiments of the present invention, the polyolefin may have a melt viscosity greater than or equal to <NUM> cPs at <NUM>, such as greater than or equal to <NUM> cPs at <NUM>, greater than or equal to <NUM> cPs at <NUM>, greater than or equal to <NUM> cPs at <NUM>, or greater than or equal to <NUM> cPs at <NUM>.

Examples of commercially available polyolefin having a melt viscosity less than or equal to <NUM> cPs at <NUM> are, for example, Aerafin <NUM> from Eastman; and RT <NUM> from Rextac.

In some embodiments of the present invention, the amount of the polyolefin of the invention is from <NUM> to <NUM>% by weight based on the total weight of the composition.

In some embodiments of the present invention, the weight ratio between the hydrogenated thermoplastic block copolymer and the polyolefin is less than or equal to <NUM>:<NUM>, preferably less than or equal to <NUM>: <NUM>, more preferably from <NUM>: <NUM> to <NUM>:<NUM>, and even more preferably from <NUM>:<NUM> to <NUM>:<NUM>.

In some embodiments of the present invention, the hot melt adhesive composition may further optionally include other additives, such as at least one wax, at least one plasticizer, at least one tackifier, at least one antioxidant, at least one pigment, at least one rheology modifier, at least one filler and any combination thereof.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one wax. The wax may be used to reduce the melt viscosity of the hot melt adhesive composition. The wax may be selected from at least one of paraffin waxes, microcrystalline waxes, polyethylene waxes, polypropylene waxes, Fischer-Tropsch waxes, oxidized Fischer-Tropsch waxes and functionalized waxes and fatty amide waxes. Examples of commercially available waxes are, for example, Sasaolwax H1 from Sasol Wax; AC-<NUM> from Honeywell; MC-<NUM> from Marcus Oil Company; Epolene C-<NUM> from Eastman Chemical; and AC-575P from Honeywell.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one plasticizer. The plasticizer is used to decrease the melt viscosity of the hot melt adhesive, impart the flexibility to the hot melt adhesive and improve the wettability of the hot melt adhesive. Preferably, the plasticizer is a paraffin oil, naphthene oil and any combination thereof. Examples of commercially available plasticizers are, for example, KN <NUM>, KN <NUM>, and KN <NUM> from PetroChina Lubricant Company; LP <NUM>, and LP <NUM> from Kukdong Oil & Chemicals; and Nyflex 222B from Nynas.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one tackifier. Preferably, the tackifier has a Ring & Ball softening point from <NUM> to <NUM>. The tackifier includes but not limited to aliphatic petroleum resin, cyclic petroleum resin, aromatic petroleum resin, gum resin, rosin ester, synthetic terpene resin, natural terpene resin and any combination thereof. Preferably, the tackifier is fully hydrogenated aliphatic tackifier. Examples of commercially available tackifiers are, for example, C100R, C100W, H130R, and H130W from Eastman; H5-<NUM> and H5-<NUM> from Henghe China; SU90, SU100, SU120 and SU130 from Kolon Industries; I-Marv P90, I-Marv P100, and I-Marv P120 from Idemitsu; Regalite R1100, Regalite R1120, and Regalite S1100 from Eastman; JH-<NUM> and JH-<NUM> from Jinhai Chengguang.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one antioxidant. The antioxidant includes but not limited to hindered phenol, phosphite, thiodipropionate and any combination thereof. Examples of commercially available antioxidants are, for example, Evernox 10GF and Evernox <NUM> from Everspring Chemical; Irganox <NUM> and Irganox <NUM> from BASF; Thanox <NUM> and Thanox <NUM> from Rianlon; Everfos <NUM> from Everspring Chemical; Iragafos <NUM> from BASF; Thanox <NUM> from Rianlon; Thanox <NUM> and Thanox DSTP from Rianlon; ADKAO <NUM> from Adeka; and Sumilizer TP-D from Sumitomo Chemical.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one pigment. The pigment includes but not limited to titanium oxide, carbon black and any combination thereof.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one rheology modifier. The rheology modifier includes but not limited to fumed silica, polyacrylates and any combination thereof.

In some embodiments of the present invention, the hot melt adhesive composition may optionally include at least one filler. The filler includes but not limited to mica, calcium carbonate, kaolin, talc, silicon dioxide and any combination thereof.

In a preferred embodiment, the hot melt adhesive composition comprises:.

the weight percentages of all components add up to <NUM>% by weight.

The hot melt adhesive composition of the present invention may be prepared by mixing the components of the hot melt adhesive composition at high temperature, such as <NUM> to <NUM>, so that all components can be fully melt and well mixed.

The melt viscosity of the hot melt adhesive composition of the present invention may be measured at a desired temperature with a <NUM># spindle, and a Brookfield hotmelt viscosity tester.

The hot melt adhesive composition of the present invention preferably has a melt viscosity less than or equal to <NUM> cPs at <NUM>. In some embodiments, the hot melt adhesive composition preferably has a melt viscosity less than or equal to <NUM> cPs at <NUM>.

The odor score of the hot melt adhesive composition of the present invention may be determined by the steps of:.

The hot melt adhesive composition of the present invention preferably has an odor score lower than <NUM>. In some embodiments, the hot melt adhesive composition preferably has an odor score less than or equal to <NUM>.

The T peel strength of the hot melt adhesive composition of the present invention may be assessed by the steps of:.

The hot melt adhesive composition of the present invention preferably has a T peel strength greater than or equal to <NUM> N for adhering PE and non-woven hydrophilic fabric when being applied at <NUM> gsm. In some embodiments, the hot melt adhesive composition preferably has a T peel strength greater than or equal to <NUM> N for adhering PE and non-woven hydrophilic fabric when being applied at <NUM> gsm.

The hot melt adhesive composition of the present invention preferably has a T peel strength greater than <NUM> N for adhering PE and non-woven hydrophobic fabric when being applied at <NUM> gsm. In some embodiments, the hot melt adhesive composition preferably has a T peel strength greater than or equal to <NUM> N for adhering PE and non-woven hydrophobic fabric when being applied at <NUM> gsm.

The hot melt adhesive composition of the present invention preferably has a T peel strength greater than or equal to <NUM> N for adhering non-woven hydrophilic fabric and non-woven hydrophobic fabric when being applied at <NUM> gsm. In some embodiments, the hot melt adhesive composition preferably has a T peel strength greater than or equal to <NUM> N for adhering non-woven hydrophilic fabric and non-woven hydrophobic fabric when being applied at <NUM> gsm.

The hot melt adhesive composition of the present invention preferably has a T peel strength greater than or equal to <NUM> N for adhering PE and tissue when being applied at <NUM> gsm. In some embodiments, the hot melt adhesive composition preferably has a T peel strength greater than or equal to <NUM> N for adhering PE and tissue when being applied at <NUM> gsm.

The present invention will be further described and illustrated in detail with reference to the following examples. The examples are intended to assist one skilled in the art to better understand and practice the present invention, however, are not intended to restrict the scope of the present invention. All numbers in the examples are based on weight unless otherwise stated.

The melt viscosity of polyolefin in the present invention was measured at <NUM>° C with a <NUM># spindle, and a Brookfield hotmelt viscosity tester.

The melt viscosity of hot melt adhesive composition in the present invention was measured in a temperature range from <NUM> to <NUM>° C with a <NUM># spindle, and a Brookfield hotmelt viscosity tester.

Weighted out <NUM> grams of hot melt adhesive and placed the hot melt adhesive in a <NUM> glass jar. Covered the glass jar with aluminum foil and heated the glass jar at <NUM> ° C for <NUM> hours. Took out the glass jar and cooled the glass jar to <NUM> ° C. Reheated the glass jar for to <NUM> ° C for <NUM> hour. Took out the glass jar and cooled the glass jar to <NUM> ° C.

Organized a group of five test panel members. The test panel members were selected with no smoking or drinking habits. Each test panel member was given a glass jar containing the identical hot melt adhesive prepared by the method stated above. The test panel member removed the aluminum foil and smelled the odor from the glass jar at a distance of <NUM> from the opening of the glass jar. Each test panel member assigned a score of the odor from the glass jar independently. The average score of the five test panel members was the odor score for the hot melt adhesive.

The rules for the test panel member to assign a score to the hot melt adhesive were:.

A PE sheet (Air permeable cast film with a thickness of <NUM> gsm from Foshan Landi) and a non-woven hydrophilic fabric sheet (Hot air non-woven fabric 2AT-<NUM> with a thickness of <NUM> gsm from Nanliu Corporation) were adhered together to form a laminate sample by applying the hot melt adhesive between the two sheets at <NUM> gsm via Signature nozzle head between <NUM> to <NUM>. The PE sheet and the non-woven hydrophilic fabric sheet were peeled from one another at an angle of <NUM>° and with a rate of <NUM>/min using Instron <NUM> tensile strength tester. The T peel test was carried out at <NUM> and <NUM>% relative humidity. The T peel test was made to the laminate sample at least <NUM> hours after the hot melt adhesive was applied. The PE sheet and the non-woven hydrophilic fabric sheet were pulled <NUM> apart and the force was recorded as the T peel strength of the hot melt adhesive for adhering PE and non-woven hydrophilic fabric.

A PE sheet (Air permeable cast film with a thickness of <NUM> gsm from Foshan Landi) and a non-woven hydrophobic fabric sheet (SS non-woven fabric with a thickness of <NUM> gsm from JOFO Nonwoven Ltd. ) were adhered together to form a laminate sample by applying the hot melt adhesive between the two sheets at <NUM> gsm via Signature nozzle head between <NUM> to <NUM>. The PE sheet and the non-woven hydrophobic fabric sheet were peeled from one another at an angle of <NUM>° and with a rate of <NUM>/min using Instron <NUM> tensile strength tester. The T peel test was carried out at <NUM> and <NUM>% relative humidity. The T peel test was made to the laminate sample at least <NUM> hours after the hot melt adhesive was applied. The PE sheet and the non-woven hydrophobic fabric sheet were pulled <NUM> apart and the force was recorded as the T peel strength of the hot melt adhesive for adhering PE and non-woven hydrophobic fabric.

A non-woven hydrophilic fabric sheet (Hot air non-woven fabric 2AT-<NUM> with a thickness of <NUM> gsm from Nanliu Corporation) and a non-woven hydrophobic fabric sheet (SS non-woven fabric with a thickness of <NUM> gsm from JOFO Nonwoven Ltd. ) were adhered together to form a laminate sample by applying the hot melt adhesive between the two sheets at <NUM> gsm via Signature nozzle head between <NUM> to <NUM>. The non-woven hydrophilic fabric sheet and the non-woven hydrophobic fabric sheet were peeled from one another at an angle of <NUM>° and with a rate of <NUM>/min using Instron <NUM> tensile strength tester. The T peel test was carried out at <NUM> and <NUM>% relative humidity. The T peel test was made to the laminate sample at least <NUM> hours after the hot melt adhesive was applied. The non-woven hydrophilic fabric sheet and the non-woven hydrophobic fabric sheet were pulled <NUM> apart and the force was recorded as the T peel strength of the hot melt adhesive for adhering non-woven hydrophilic fabric and non-woven hydrophobic fabric.

A PE sheet (Air permeable cast film with a thickness of <NUM> gsm from Foshan Landi) and a tissue (cellulose tissue with a thickness of <NUM> gsm from Zhongzhi) were adhered together to form a laminate sample by applying the hot melt adhesive between the two sheets at <NUM> gsm via Signature nozzle head between <NUM> to <NUM>. The PE sheet and the tissue were peeled from one another at an angle of <NUM>° and with a rate of <NUM>/min using Instron <NUM> tensile strength tester. The T peel test was carried out at <NUM> and <NUM>% relative humidity. The T peel test was made to the laminate sample at least <NUM> hours after the hot melt adhesive was applied. The PE sheet and the tissue were pulled <NUM> apart and the force was recorded as the T peel strength of the hot melt adhesive for PE and tissue.

Hot melt adhesive composition samples were prepared, according to Table <NUM>, by mixing the components selected from:.

In Table 2A and Table 2B, the melt viscosity of the hot melt adhesive samples is reported. In order to coat the hot melt adhesive properly onto the substrates, the melt viscosity of the hot melt adhesive usually is required to be less than or equal to <NUM> cPs. Therefore, the hot melt adhesive samples in Example <NUM> to <NUM> can all be applied at the temperature of <NUM>° C.

When polyolefin with a melt viscosity greater than <NUM> cPs at <NUM>° C were used in the hot melt adhesive samples as in Example <NUM> and <NUM>, the melt viscosity of the hot melt adhesive samples increased to over <NUM> cPs at the temperature of <NUM>° C. Therefore, the hot melt adhesive samples in Example <NUM> and <NUM> cannot be properly applied at the temperature of <NUM>° C.

When SEBS with a melt index less than <NUM>/<NUM> at <NUM>° C/<NUM> was used in the hot melt adhesive sample as in Example <NUM>, the melt viscosity of the hot melt adhesive sample increased greatly at the temperature of <NUM>° C. Therefore, the hot melt adhesive sample in Example <NUM> cannot be properly applied at the temperature of <NUM>° C.

The melt viscosity of the SIS or SBS based adhesive sample in Example <NUM> or <NUM> was also high at the temperature of <NUM>° C. Therefore, the hot melt adhesive samples in Example <NUM> and <NUM> cannot be properly applied at the temperature <NUM>° C.

When the weight ratio between the hydrogenated thermoplastic block copolymer and the polyolefin was less than <NUM>:<NUM>, the melt viscosity of the hot melt adhesive samples in Example <NUM> to <NUM> was less than <NUM> cPs at <NUM>° C. It was further found that when the weight ratio between the hydrogenated thermoplastic block copolymer and the polyolefin was in the range of <NUM>:<NUM> to <NUM>:<NUM>, the melt viscosity of the hot melt adhesive sample was lower than <NUM> cPs at the temperature of <NUM>° C as shown in Example <NUM>. Therefore, the hot melt adhesive sample in Example <NUM> can even be applied at the temperature of <NUM>° C.

In Table <NUM>, the odor scores of the hot melt adhesive samples are reported. It was shown that SEBS based adhesive samples in Example <NUM> to <NUM> had better odor score compared with the SIS or SBS based adhesive sample in Example <NUM> or <NUM>.

In Table <NUM>, the T peel strength of the hot melt adhesive samples is reported. In order to coat the hot melt adhesive samples to the substrates of the laminate samples properly, the hot melt adhesive samples in Example <NUM>, <NUM>, <NUM> and <NUM> were applied at the temperature of <NUM>° C, <NUM>° C, <NUM>° C and <NUM>° C respectively. It was shown that the SEBS based adhesive samples in Example <NUM> and <NUM> have better T peel strength than the SIS or SBS based adhesive sample in Example <NUM> or <NUM>. It was also found that when the weight ratio between the hydrogenated thermoplastic block copolymer and the polyolefin was in the range of <NUM>:<NUM> to <NUM>:<NUM>, the T peel strength of the hot melt adhesive was even further improved as shown in Example <NUM>.

Claim 1:
A hot melt adhesive composition comprising, by weight based on the total weight of the composition:
<NUM> to <NUM> wt.% of at least one hydrogenated thermoplastic block copolymer with a melt index greater than or equal to <NUM>/<NUM> as determined according to ASTM D-<NUM> at <NUM>/<NUM>, wherein the hydrogenated thermoplastic block copolymer is a copolymer of a vinyl-based aromatic hydrocarbon with a conjugated diene; and,
<NUM> to <NUM>% of at least one polyolefin with a melt viscosity less than or equal to <NUM> mPa·s (<NUM> cPs) at <NUM>, wherein said at least one polyolefin is selected from polyethylene, polypropylene, polybutene, and the copolymers and terpolymers thereof.