Water-based Polyurethane Adhesive Composition
Technical field
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The present invention relates to a water-based polyurethane adhesive composition, to a cured product obtained from said composition, as well as to an article comprising said cured product or assembled using said composition.
Background of the invention
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Nowadays, water-based adhesives are replacing solvent-based adhesives due to environmental protection issues. Water-based polyurethane (PU) adhesives use water as the solvent or dispersant, PU particles are dispersed in the water. Compared with solvent-based PU adhesives, water-based PU adhesives have advantages like no toxicity, nonflammable, low volatiles (VOCs) , low cost and so on.
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Commercially available water-based PU dispersion (PUD) adhesives usually have an activation temperature of from 50 to 60 ℃, from 80-100 ℃. Such a high activation temperature hinders their use in bonding temperature-sensitive substrates, such as foams, films, synthetic leathers in suitcases, shoes, textile products. There are some water-based PUD adhesives having lower activation temperature, but they cannot achieve both excellent green bond strength and excellent final bond strength.
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Therefore, there is a need in the art to develop a water-based PU adhesive composition with low activation temperature but can achieve both excellent green bond strength and excellent final bond strength.
Summary of the invention
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After intensive study, the inventors of the present application have found that, by specifically selecting the weight ratio between the soft segment and the hard segment as well as the weight average molecular weight (Mw) of the polyurethane polymer, the water-based polyurethane adhesive composition can be activated at a low temperature and at the same time can achieve both excellent green bond strength and excellent final bond strength.
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In the first aspect, the present application provides a water-based polyurethane adhesive composition comprising:
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(a) a polyurethane polymer comprising a soft segment derived from a polyester polyol and a hard segment derived from a polyisocyanate; wherein the weight ratio between
the soft segment and the hard segment is greater than 5.6, and the weight average molecular weight (Mw) of the polyurethane polymer is no more than 20000 g/mol;
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(b) water;
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(c) optionally, a thickening agent,
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(d) optionally, a defoamer; and
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(e) optionally, a mattering agent.
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In the second aspect, the present application provides an activated product obtained from the composition of the first aspect.
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In the third aspect, the present application provides an article comprising the cured product of the second aspect or assembled using the composition of the first aspect.
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In the fourth aspect, the present application provides a method for bonding substrates with the composition according to the first aspect, comprising:
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(i) applying the composition onto one or two substrates,
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(ii) activating the composition at a temperature of no more than 40 ℃, such as 35 ℃, for 3-4 mins,
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(iii) mating and pressing the two substrates together.
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The advantages of the present invention include:
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(1) The composition of the present application can be activated at low temperature, such as lower than 40 ℃, like 35 ℃, 36 ℃, 37 ℃ 38 ℃, 39 ℃, and
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(2) The activated products of the composition have both excellent green bond strength and excellent final bond strength.
Detailed description of the invention
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It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention. Each aspect so described may be combined with any other aspect (s) 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.
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Unless specified otherwise, in the context of the present invention, the terms used are to be construed in accordance with the following definitions.
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Unless specified otherwise, all wt. %or %by weight values quoted herein are percentages by weight.
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Unless specified otherwise, as used herein, the terms “a” , “an” and “the” include both singular and plural referents.
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The terms “comprising” and “comprises” 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.
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The term “consisting essentially of” as used herein means that the listed components constitute main body of the composition, for example, at least 90%by weight of the composition.
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The term “consisting of” as used herein is close-ended and exclude additional, non-recited intentionally added members, elements or process steps.
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The term “at least one” or “one or more” used herein to define a component refers to the type of the component, and not to the absolute number of molecules.
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The terms “about” , “around” and the like used herein in connection with a numerical value refer to the numerical value ±10%, preferably ±5%. All numerical values herein should be interpreted as being modified by the term “about” .
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The term “water-based polyurethane adhesive composition” used herein means that the composition comprises less than 0.5 wt%, preferably less than 0.1wt%, more preferably less than 0.01wt%, most preferably 0%of organic solvent (s) .
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Unless specified otherwise, the recitation of numerical end points includes all numbers and fractions subsumed within the respective ranges, as well as the recited end points.
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Unless otherwise defined, all terms used in the present invention, including technical and scientific terms, have the meaning as commonly understood by one of the ordinary skilled in the art to which this invention belongs.
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Hereinafter the water-based polyurethane adhesive composition will be described in detail.
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The water-based polyurethane adhesive composition comprises, consists essentially of or
consists of:
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(a) a polyurethane polymer comprising a soft segment derived from polyester polyol and a hard segment derived from a polyisocyanate; wherein the weight ratio between the soft segment and the hard segment is greater than 5.6 and the weight average molecular weight of the polyurethane polymer is no more than 20000 g/mol;
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(b) water;
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(c) optionally, a thickening agent,
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(d) optionally, a defoamer; and
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(e) optionally, a mattering agent.
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Component (a) : polyurethane polymer
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The polyurethane (PU) polymer used herein necessarily comprises a soft segment derived from a polyester polyol, preferably from a polyester diol, and a hard segment derived from a polyisocyanate, preferably from a diisocyanate; and the following conditions have to be satisfied: (1) the weight ratio between the soft segment and the hard segment is greater than 5.6, such as greater than 5.65, and (2) the Mw of the polyurethane polymer is no more than 20000 g/mol.
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The term “soft segment derived from a polyester polyol” and term “hard segment derived from a polyisocyanate” used herein mean that during the PU preparation, a polyester polyol reacts with a polyisocyanate to form the PU polymer, and the polyester polyol may remove some atom (s) and the polyisocyanate may acquire some atom (s) during the reaction and the remaining part of the polyester polyol constitutes the soft segment and the remaining part the polyisocyanate constitutes the hard segment.
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The PU polymer suitable for the present application is a non-reactive PU polymer, which does not contain any reactive -NCO group in the molecular chain. Therefore, the PU polymer is obtained by reacting slightly molar excess of the polyester polyol with the polyisocyanate to ensure no reactive -NCO group left in the chain.
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The PU polymer suitable for the present application may optionally contain other building blocks, but preferably said other building blocks are contained in an amount of less than 5wt%, preferably less than 4wt%, less than 3wt%, less than 2wt%, less than 1wt%, or less than 0.5wt%, based on the total weight of the PU polymer.
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Preferably, the polyester polyol used herein is a polyester diol preferably selected from
poly (ethylene adipate) diol (PEA diol) , poly (butylene adipate) diol (PBA diol) , poly (neopentylene adipate) diol (PNA diol) , poly (hexylene adipate) diol (PHA diol) , poly (propylene adipate) diol (PPA diol) and combinations thereof. These polyester diols may have a molecular weight (Mw) in the range of from 800 to 3000 g/mol, such as 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900 g/mol.
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The weight average molecular weight (Mw) mentioned in the present application is determined through gel permeation chromatogrphy (GPC) .
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Preferably, the polyisocyanate used herein is selected from 4, 4’ -diphenylmethane diisocyanate (MDI) , isophorone diisocyanate (IPDI) , Toluene diisocyanate (TDI) , Hexamethylene Diisocyanate (HDI) , dicyclohexylmethane-4, 4'-diisocyanate (HMDI) and combinations thereof.
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The PU polymer suitable for the present application can be produced with any known method in the art, for example, catalyst may or may not be used during the preparation, a chain extender may or may not be used during the preparation.
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Merely listed as examples, the PU polymer suitable for the present application can be obtained by reacting PBA diol with HDI, or by reacting PBA diol with a mixture of HDI and IPDI, or by reacting PBA diol with MDI, or by reacting PBA diol with TDI, or by reacting PBA diol with HMDI, by reacting PEA diol with HDI, or by reacting PEA diol with a mixture of HDI and IPDI, or by reacting PEA diol with MDI, or by reacting PEA diol with TDI, or by reacting PEA diol with HMDI, or by reacting PNA diol with HDI, or by reacting PNA diol with a mixture of HDI and IPDI, or by reacting PNA diol with MDI, or by reacting PNA diol with TDI, or by reacting PNA diol with HMDI, or by reacting PHA diol with HDI, or by reacting PHA diol with a mixture of HDI and IPDI, or by reacting PHA diol with MDI, or by reacting PHA diol with TDI, or by reacting PHA diol with HMDI, or by reacting PPA diol with HDI, or by reacting PPA diol with a mixture of HDI and IPDI, or by reacting PPA diol with MDI, or by reacting PPA diol with TDI, or by reacting PPA diol with HMDI, and the like.
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One condition that the PU polymer suitable for the present application has to be satisfied is that the weight ratio between the soft segment and the hard segment is greater than 5.6, preferably greater than 5.65, but is preferably less than 10, less than 9, less than 8, less than 7, or less than 6.5.
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Another condition that the PU polymer suitable for the present application has to be satisfied
is that the Mw of the PU polymer is no more than 20000 g/mol, preferably, the Mw of the PU polymer is greater than 15000 g/mol, such as greater than 16000 g/mol, greater than 17000 g/mol, or greater than 18000 g/mol, but no more than 20000 g/mol, preferably no more than 19500 g/mol.
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The component (a) the PU polymer may be comprised in the composition in an amount of 40 to 55 wt%, or 45 to 50 wt%, such as 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 wt%, or any ranges between two numbers listed above, based on total weight of the composition.
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Component (b) : water
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Water constitutes main part of the composition of the present application. Water may be mixed with the PU polymer upon preparation, and/or water may be partially mixed with the PU polymer in advance forming a PU water dispersion (PUD) , then adding water according to practical need upon composition preparation.
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Water, no matter added upon preparation of the composition or mixed with the PU polymer in advance to form a PUD, is may be comprised in the composition in an amount of 45 to 60wt%, or 50 to 55 wt%, such as 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 wt%, or any ranges between two numbers listed above, based on total weight of the composition.
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Component (c) : thickening agent
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The composition of the present application may optionally comprise a thickening agent according to the requirements of application use.
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The purpose of the thickening agent is to increase the viscosity of the composition so as to facilitate the coating or application use. Conventional thickening agents in the art can be used herein without particular limitations. Preferably, polyurethane polymer having similar building units with the component (a) can be used, but the weight ratio between the soft segment and the hard segment and the Mw of the polyurethane polymer of the thickening agent are not limited as long as it can achieve the purpose of thickening.
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If present, amount of the thickening agent in the composition of the present application may be adjusted according to practical needs without particular limitation as long as the desired effect of the composition or of the adhesive is not negatively affected. Preferably, the
component (c) the thickening agent may be comprised in the composition in an amount of 0.5 to 2 wt%, or 0.6 to 1.5 wt%, such as 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 wt%, or any ranges between two numbers listed above, based on total weight of the composition.
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Component (d) : defoamer
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The composition of the present application may optionally comprise a defoamer so as to decrease the foam formation during the composition preparation and/or during application. Conventional defoamers in the art can be used herein without particular limitations.
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If present, amount of the defoamer in the composition of the present application may be adjusted according to practical needs without particular limitation as long as the desired effect of the composition or of the adhesive is not negatively affected. Preferably, the component (d) the defoamer may be comprised in the composition in an amount of 0.01 to 0.2 wt%, or 0.05 to 0.15 wt%, such as 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.12, 0.14, 0.16, 0.18 wt%, or any ranges between two numbers listed above, based on total weight of the composition.
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Component (e) : matting agent
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The composition of the present application may optionally comprise a matting agent so as to decrease the light reflection effect of the adhesive. Conventional mattering agents in the art can be used herein without particular limitations.
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If present, amount of the mattering agent in the composition of the present application may be adjusted according to practical needs without particular limitation as long as the desired effect of the composition or of the adhesive is not negatively affected. Preferably, the component (e) the mattering agent may be comprised in the composition in an amount of 0.01 to 0.2 wt%, or 0.05 to 0.15 wt%, such as 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.12, 0.14, 0.16, 0.18 wt%, or any ranges between two numbers listed above, based on total weight of the composition.
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In the second aspect, the present application also provides an activated product obtained from the composition of the present application. The activated product of the composition can be obtained via heating the applied composition at a temperature of no more than 40 ℃, such as 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃. The duration of heating activation can be for examples 3-4 mins.
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In the third aspect, the present application also provides an article comprising said activated product or assembled using the composition of the present application. For example, the article can be shoes, soles, textile products and suitcases.
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In the fourth aspect, the present application also provides a method for bonding substrates together with the composition of the present application, said method comprises, consists essentially of or consists of steps of:
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(i) applying the composition onto one or two substrates,
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(ii) activating the composition at a temperature of no more than 40 ℃, such as 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃, for 3-4mins,
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(iii) mating and pressing the two substrates together.
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Examples
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The invention will now be described by way of the following examples. The following examples are intended to assist one skilled in the art to better understand and practice the present invention. The scope of the invention is not limited by the examples but is defined in the appended claims. All parts and percentages are based on weight unless otherwise stated.
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Materials used in the examples:
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Test methods of green bond strength and final bond strength:
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Applying the composition on two rubber slabs with the size of 20mm (width) X 100mm (length) and heating the slabs at about 35℃ for 3 mins, then attaching two slabs and pressing. The pressure is 20 kgf and pressing time is 15 seconds. The green bond strength is tested by 180° peeling within 1 min after pressing using tensile machine Instron LEGEND 2344 under a peeling speed of tensile machine being 150 mm/min, and the final bond strength is tested by 180° peeling 24 hours after pressing using tensile machine Instron LEGEND 2344 under a peeling speed of tensile machine being 150 mm/min.
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Evaluation criteria:
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When the green bond strength is greater than 2.5 kgf/cm, it is marked as excellent. When the final bond strength is greater than 4.0 kgf/cm, it is marked as excellent.
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Examples 1 to 2 and Comparative Examples 1 to 4 (EX 1 to 2 and CE 1 to 4)
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All ingredients listed in Table 1 were mixed using a mixer to form each composition. Performance of each composition was tested using the above-mentioned methods.
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Table 1:
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It can be seen from Table 1 that when the weight ratio between the soft segment and the hard segment of the PU polymer is greater than 5.6 and the Mw of the PU polymer is less than 20000 g/mol (Ex1 to Ex2) , the activated PU adhesive can achieve both excellent green bond strength and excellent final bond strength; when the weight ratio between the soft segment and the hard segment of the PU polymer is less than 5.6, both excellent green bond strength and excellent final bond strength (CE1 to CE2) are not achieved, or excellent green bond strength is not achieved (CE3) ; when the weight ratio between the soft segment and the hard segment of the PU polymer is greater than 5.6 but the Mw of the PU polymer is greater than 20000 g/mol (CE4) , excellent green bond strength is not achieved.
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Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.