WO2018176300A1

WO2018176300A1 - A novel mdi-based prepolymer binder for moisture curing binder application

Info

Publication number: WO2018176300A1
Application number: PCT/CN2017/078710
Authority: WO
Inventors: Jiawen Xiong; Xiangyang Tai; Huan CHEN; Jiang Li; Juelin LIU
Original assignee: Dow Global Technologies Llc
Priority date: 2017-03-30
Filing date: 2017-03-30
Publication date: 2018-10-04
Also published as: WO2018182912A1

Abstract

The present disclosure provides a novel MDI-based prepolymer binder which is a reaction product of an MDI prepolymer, or a mixture of an MDI prepolymer and an MDI monomer, with a compound having Formula (I) or Formula (II).

Description

A NOVEL MDI-BASED PREPOLYMER BINDER FOR MOISTURE CURING BINDER APPLICATION

FIELD OF THE DISCLOSURE

The present disclosure relates to a novel MDI-based prepolymer binder, which is specifically designed for moisture curing binder applications, and is especially suitable for sports track applications.

INTRODUCTION

Moisture curing isocyanate prepolymer, which cures by reaction with moisture, is dominating in various binder applications. Its usage in binder for sports track is a typical application. In a conventional operation, the binder is first blended with rubber particles to coat the particle surface, and the coated rubber particles are then applied on field to form a rubber layer. The rubber layer will be further pressed and trimmed to suit different applications, and allowed for further curing with the moisture in the environment until its completion. Moisture curing isocyanate prepolymer, in this regard, has a relatively low viscosity that ensures good wettability on the surface of rubber particles, which helps the reaction between isocyanate end groups and the moisture in the environment, which further helps the formation of polymer network so that enables its good mechanical strength and adhesion to rubber particles. The prepolymer is a reaction product of isocyanates and polyols. The amount of NCO groups in the isocyanates may be excessive to the OH groups in the polyols, so that the excessive NCO group may further react with the moisture in the environment. The reaction kinetics between the excessive NCO group with the moisture has to be mild, and long enough to provide a sufficient operation time.

Presently, toluene diisocyanate (TDI) based prepolymer is widely used in these applications, especially in sports track applications. However, TDI residual in the final sports track may be concerned extremely harmful to the environment since TDI has a high vapor pressure of 0.01 mmHg at 25℃.

Considering the above health hazard, people in the art are trying to use methylene diphenyl diisocyanate (MDI) to replace TDI for sports track applications. MDI is classified as “low toxic” by the European Community and has a relatively low vapor pressure at 25℃so that it residual in the final sports track is not easy to go out and harm the environment.

However, the reactivity of NCO end group on MDI prepolymer with moisture is much higher than that of NCO end group on TDI prepolymer. As the consequence, viscosity is built up too fast, when preparing MDI-based prepolymer binders, to support a sufficient operation time in sports track application and others.

It is therefore, still desired in the art a novel MDI-based prepolymer binder for various binder applications including sports track.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a novel MDI-based prepolymer binder which is a reaction product of an MDI prepolymer, or a mixture of an MDI prepolymer and an MDI monomer, with a compound having the following Formula (I) or Formula (II) :

R₁, R₂ and R₃ may be identical, or different, and are each individually selected from H, and C_aH_b, and a is an integral of from 1 to 40, and b is an integral of from 2a-4 to 2a+1； R₁, R₂, and R₃ are not all H；

and R is represented by (OC_mH_2m) _n, and m is an integral from 2 to 5, and n is an integral from 3 to 40.

The present disclosure further provides an elastomeric composite comprising the MDI-based prepolymer binder.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure provides a novel MDI-based prepolymer binder for binder applications, especially for sports track. The novel MDI-based prepolymer binder is the reaction product of an MDI prepolymer, or a mixture of an MDI prepolymer and an MDI monomer, with a compound having the following Formula (I) or Formula (II) .

wherein R₁, R₂ and R₃ may be identical, or different, and are each individually selected from H, and C_aH_b, wherein a is an integral of from 1 to 40, or from 5 to 30, or from 10 to 25, and b is an integral of from 2a-4 to 2a+1, wherein R₁, R₂, and R₃ are not all H.

R is represented by (OC_mH_2m) _n, wherein m is an integral from 2 to 5, and n is an integral from 3 to 40, or from 4 to 30, or from 5 to 20.

MDI monomers could be used in the present disclosure comprise 4, 4-MDI and 2, 4-MDI, and the mixture thereof.

MDI prepolymers are reaction products of a polyol with excessive MDI monomer. There are two or more NCO end groups in one MDI prepolymer molecule. Polyol is an alcohol containing multiple hydroxyl groups. The MDI prepolymers may also be referred to isocyanate-terminated MDI prepolymers. Depending on its synthetic route and chemical structure, polyols used in this disclosure include, but are not limited to, polyether polyols, polyester polyols, polycarbonate polyols, and the mixtures thereof. Suitable examples of the polyol include polyether polyols, and its mixtures polyester polyols.

Polyether polyols are the addition polymerization products and the graft products of ethylene oxide, propylene oxide, tetrahydrofuran, and butylene oxide, the condensation products of polyhydric alcohols, and any combinations thereof. Suitable examples of the polyether polyols include, but are not limited to, polypropylene glycol (PPG) , polyethylene glycol (PEG) , polybutylene glycol, polytetramethylene ether glycol (PTMEG) , and any combinations thereof. In some embodiments, the polyether polyols are the combinations of PEG and at least one another polyether polyol selected from the above described addition polymerization and graft products, and the condensation products. In some embodiments, the polyether polyols are the combinations of PEG and at least one of PPG, polybutylene glycol, and PTMEG.

The polyester polyols are the condensation products or their derivatives of diols, and dicarboxylic acids and their derivatives.

Suitable examples of the diols include, but are not limited to, ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 2-methyl-1, 3-propandiol, 1, 3-butanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, 3-methyl-1, 5-pentandiol, and any combinations thereof. In order to achieve a polyol functionality of greater than 2, triols and/or tetraols may also be used. Suitable examples of such triols include, but are not limited to, trimethylolpropane and glycerol. Suitable examples of such tetraols include, but are not limited to, erythritol and pentaerythritol.

Dicarboxylic acids are selected from aromatic acids, aliphatic acids, and the combination thereof. Suitable examples of the aromatic acids include, but are not limited to, phthalic acid, isophthalic acid, and terephthalic acid； while suitable examples of the aliphatic acids include, but are not limited to, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methyl succinic acid, 3, 3-diethyl glutaric acid, and 2, 2-dimethyl succinic acid. Anhydrides of these acids can likewise be used. For the purposes of the present disclosure, the anhydrides are accordingly encompassed by the expression of term “acid” . In some embodiments, the aliphatic acids and aromatic acids are saturated, and are respectively adipic acid and isophthalic acid. Monocarboxylic acids, such as benzoic acid and hexane carboxylic acid, should be minimized or excluded.

Polyester polyols can also be prepared by addition polymerization of lactone with diols, triols and/or tetraols. Suitable examples of lactone include, but are not limited to, caprolactone, butyrolactone and valerolactone. Suitable examples of the diols include, but are not limited to, ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 2-methyl 1, 3-propandiol, 1, 3-butanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, 3-methyl 1, 5-pentandiol and any combinations thereof. Suitable examples of triols include, but are not limited to, trimethylolpropane and glycerol. Suitable examples of tetraols include erythritol and pentaerythritol.

Polycarbonate polyols are molecules with a carbonate backbone and OH end groups. It could be produced through reaction between a diol with phosgene, or through copolymerization reaction between CO₂ and alkylene oxide.

No matter the backbone chemical structure is, the polyols used in the present disclosure have a number average molecular weight Mn of from 400 to 4000 g/mol, or from 750 to 3500 g/mol, or from 800 to 3000 g/mol； and a nominal hydroxyl functionality of from 2 to 8, or from 2 to 5, or from 2 to 4.

The preparation of the MDI prepolymer is in any way known to those of ordinary skill in the art, and includes condensation polymerization. The stoichiometry of the MDI prepolymer formulation disclosure is such that the diisocyanate is present in excess, and the MDI prepolymer is NCO group terminated. In some embodiments, the molar ratio of NCO group to OH group is much higher than 2, therefor the product is the mixture of MDI prepolymer and unreacted MDI monomer. The stoichiometry ratio is also referred to as an isocyanate index, which is the equivalents of isocyanate groups (i.e., NCO moieties) present, divided by the total equivalents of isocyanate-reactive groups (e.g., OH moieties) present. Considered in another way, the isocyanate index is the ratio of the isocyanate groups over the isocyanate reactive hydrogen atoms present in a formulation, given as a ratio and may be given as a percentage when multiplied by 100. Thus, the isocyanate index expresses the isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.

In some embodiments, pure 2, 4-MDI is used, and the molar ratio of NCO group to OH group is equal to 2, and there is no or just trace unreacted MDI monomer in the so synthesized prepolymer. The so synthesized prepolymer could be mixed with MDI monomer to adjust the overall NCO％in the mixture. In some embodiments, the MDI prepolymer has an isocyanate content (also known as weight ％NCO, as measured by ASTM D2572) of from 5 to 25％, or from 7 to 20％, or from 8 to 15％.

Organic solvent is preferably not used in the preparation of the MDI prepolymer.

In some embodiments, the compound having Formula (I) or Formula (II) is present from 5 to 40wt％, or from 8 to 30wt％, or from 10 to 25wt％, based on total weight of formulation for preparing the MDI-based prepolymer binder.

The preparation of the novel MDI-based prepolymer binder is in any way known to those of ordinary skill in the art. In some embodiments, it is synthesized by mixing MDI prepolymer with at least one compounds selected from the group consisting of the compounds of Formula (I) or formula (II) and conducting the reaction to form urethane bond in any way known to those of ordinary skill in the art, by optionally adding MDI monomer to adjust NCO％. In some embodiments, it is synthesized by mixing the mixture of MDI prepolymer with MDI monomer with at least one of the compounds selected from the compounds having Formula (I) or formula (II) and conducting the reaction to form urethane bond in any way known to those of ordinary skill in the art, by optionally adding additional MDI monomer to adjust NCO％. In some embodiments, it is synthesized by mixing MDI monomer with at least one of the compounds selected from the compounds having Formula (I) or formula (II) and conducting the reaction to form urethane bond in any way known to those of ordinary skill in the art, by adding MDI prepolymer and optional MDI monomer to adjust NCO％.

Optionally, from 0.5 to 10wt％, or from 1 to 8wt％, or from 2 to 6wt％, based on total weight of the MDI-based prepolymer binder, an aliphatic isocyanate crosslinker is also used in the preparation of the MDI-based prepolymer binder. The aliphatic isocyanate crosslinker may be an aliphatic diisocyanate such as hexamethylene diisocyanate (HDI) ； a trimer of such diisocyanate； an aliphatic triisocyanate； and also a polymer derived from these homopolymerized or copolymerized monomers, or derived from the addition of a polyol or of a polyamine with one or more of these monomers, with the polyol or the polyamine possibly being a polyether, a polyester, a polycarbonate, or a polyacrylate.

In some embodiments, the aliphatic isocyanate crosslinker has an NCO functionality equal to or above 3.

The MDI-based prepolymer binder, which is moisture curable, is formulated to be liquid at 25℃., and is a liquid when used to wet rubber particles to produce elastomeric composites.

An elastomeric composite is formed by mixing the moisture-curable MDI-based prepolymer binder with particles of a natural or synthetic rubber, and curing the MDI-based prepolymer binder. The rubber particles may be, for example, a vulcanized rubber, a polyurethane elastomer, an elastomeric polymer or copolymer of a diene such as butadiene homopolymers or styrene-butadiene block copolymers, very low density ethylene-alpha-olefin copolymer. Virgin material can be used, but for cost reasons it is often preferably to use reclaimed material such as shredded or ground tires, tire tubes, polyurethane foam, gasket material, playgrounds, and the like. The elastomer particles suitably have a longest dimension of no greater than about 20 mm, preferably no greater than about 15 mm and more preferably no greater than about 10 mm. For convenience of handling and processing, it is preferred that the particles are at least 1 mm, and preferably at least 3 mm, in at least one dimension.

The ratios of the moisture-curable MDI-based prepolymer binder and the elastomeric particles can range from about 1: 99 to about 50: 50 by weight. A preferred ratio is from 3: 97 to about 40: 60. A still more preferred ratio is from 5: 95 to about 25: 75.

Mixing can be done in any convenient fashion that permits the surfaces of the elastomeric particles to become wetted with the prepolymer. The mixing step is generally conducted at a temperature of from about 0 to about 40℃., although higher temperatures can be used during the mixing step if desired.

Curing is performed by exposing the resulting mixture of particles and moisture-curable MDI-based prepolymer binder to moisture. This is mainly done in at least two ways. In one approach, the moisture is simply atmospheric moisture, which comes into contact with the mixture and reacts with the isocyanate groups. In the other main approach, liquid water and/or steam is added into the mixture of particles and moisture-curable MDI-based prepolymer binder. In the latter case, the water can be mixed with the moisture-curable MDI-based prepolymer binder or with the elastomeric composites just before those components are themselves combined, or water can be added after the elastomeric composites have been wetted with the moisture-curable MDI-based prepolymer binder.

Curing can be performed at ambient temperature, or at some elevated temperature, such as up to 80℃.

In certain applications, such as playground or other outdoor installations, the elastomeric composites wetted with the moisture-curable binder are spread upon the ground, leveled and smoothed, and then allowed to cure at ambient temperature, typically with atmospheric moisture. Water may be sprayed onto the spread mixture if desired or necessary (as may be the case in a dry climate or under high temperature conditions) in order to speed the cure. In installations of this type, a certain amount of open time is needed, so that the mixture of elastomeric composites and moisture-curable resin composition remains workable long enough for the mixing, spreading, leveling and smoothing steps can be performed.

In another curing approach, the composites wetted with the moisture-curable MDI-based prepolymer binder are transferred to a large drum mold, where the curing step is performed. In this case, it is more common to add liquid water or steam to the wetted composites, to promote a faster cure. The mold may be heated if desired to speed the cure in this type of application. Upon completion of the cure, the cured mass is removed from the mold, and then can be spirally cut or shaved to form mats of a desired thickness. The mats can be fabricated further to produce a variety of articles such as gaskets, gymnasium mats, carpet underlayment, or other sealing or cushioning products.

A third curing approach is to cure the composites wetted with the moisture-curable MDI-based prepolymer binder in a mold whose internal dimensions match those needed of the final product. The mold may contain a substrate to which the resulting cushion is to be attached, as is the case in producing cushion-backed carpet tile. In this case, water or steam can be added to the wetted composites to speed the cure, and the mold may be heated for the same reason.

In any of these curing approaches, the wetted composites may be more or less tightly compacted. Higher compaction leads to a smaller void volume, a higher density product and typically a firmer product. Less compaction can lead to greater void volume, lower product densities and a softer product. Void volume is also affected by the ratios of moisture-curable MDI-based prepolymer binder and elastomeric composites； with higher ratios (relatively more of the MDI-based prepolymer binder) typically leading to lower void volumes, as greater quantities of the liquid prepolymer also the spaces between the particles to become more completely filled. Void volume in the final product may be from zero to 85％, but are more typically no greater than 30％.

EXAMPLES

I. Raw materials:

Raw materials and components used in this disclosure are listed below.

II. Test methods

(a) Reactivity evaluation: 1.0g sample MDI-based prepolymer binder was placed onto an aluminum plate, and was immediately put into an 80℃ oven of 85％humidity. Its tack free time was recorded.

(b) Sports track sample for evaluating mechanical properties: 245g rubber particles, purchased from Nanjing Feeling Rubber &Plastic Produces Co., Ltd., and 35g MDI-based prepolymer binder examples were mixed until a uniform mixture was formed by mechanical stirring. The mixture was poured into a 20 cm × 20 cm × 1 cm metal mold. Then, the filled mold was moved into an 80℃ oven of 85％humidity for curing. 8 hours later, the mixture was taken out from the mold and kept in the same oven for continuous curing. In another 8 hours, the mixture was taken out from the oven for mechanical property test.

III. Examples

Inventive Example 1 (IE1)

14.25g C₁₈H₃₇- (OC₃H₆) ₈-OH, purchased from Jiangsu Haian Petrochemical Plant, 5g DESMODUR^TM N 3300A crosslinker, and 80.75g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) were mixed with mechanical stirring to prepare the Inventive MDI-based prepolymer binder Example 1 (IE1) . The Inventive MDI-based prepolymer binder Example 1 was prepared and used for the tests.

Inventive Example 2 (IE2)

80.75g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) was charged into a three-neck flask (250ml) with a constant pressure drop funnel, nitrogen inlet and mechanical stirring, and heated to 60℃. 14.25g C₁₈H₃₇- (OC₃H₆) ₈-OH was dropped into the MDI prepolymer for 30 minutes, and reacted for further 20 minutes at 60℃. Then 5g DESMODUR^TM N 3300A crosslinker was immediately added into the flask and the mixture was being continuously stirred for several minutes to prepare the Inventive MDI-based prepolymer binder Example 2 (IE2) . The prepared Inventive MDI-based prepolymer binder Example 2 was cooled down and poured into a plastic container for storage. The whole process was operated under nitrogen atmosphere.

Inventive Example 3 (IE3)

76g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) was charged into a three-neck flask (250ml) with a constant pressure drop funnel, nitrogen inlet and mechanical stirring, and heating to 60℃. 19g C₁₈H₃₇- (OC₃H₆) ₈-OH was dropped into the MDI prepolymer for 30 minutes, and reacted for further 20 minutes at 60℃. Then 5g DESMODUR^TM N 3300A crosslinker was immediately added into the flask and the mixture was being continuously stirred for several minutes to prepare the Inventive MDI-based prepolymer binder Example 3 (IE3) . The prepared Inventive MDI-based prepolymer binder Example 3 was cooled down and poured into a plastic container for storage. The whole process was operated under nitrogen atmosphere.

Inventive Example 4 (IE4)

76g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) was charged into a three-neck flask (250ml) with a constant pressure drop funnel, nitrogen inlet and mechanical stirring, and heating to 60℃. 19g C₁₈H₃₇- (OC₃H₆) ₁₅-OH was dropped into the MDI prepolymer for 30 minutes, and reacted for further 20 minutes at 60℃. Then 5g DESMODUR^TM N 3300A crosslinker was immediately added into the flask and the mixture was being continuously stirred for several minutes to prepare the Inventive MDI-based prepolymer binder Example 4 (IE4) . The prepared Inventive MDI-based prepolymer binder Example 4 was cooled down and poured into a plastic container for storage. The whole process was operated under nitrogen atmosphere.

Inventive Example 5 (IE5)

64.4g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) was charged into a three-neck flask (250ml) with a constant pressure drop funnel, nitrogen inlet and mechanical stirring, and heating to 60℃. 27.6g C₁₈H₃₇- (OC₃H₆) ₁₅-OH was dropped into the MDI prepolymer for 30 minutes, and reacted for further 20 minutes at 60℃. Then 8g DESMODUR^TM N 3300A crosslinker was immediately added into the flask and the mixture was being continuously stirred for several minutes to prepare the Inventive MDI-based prepolymer binder Example 5 (IE5) . The prepared Inventive MDI-based prepolymer binder Example 5 was cooled down and poured into a plastic container for storage. The whole process was operated under nitrogen atmosphere.

Inventive Example 6 (IE6)

80g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) was charged into a three-neck flask (250ml) with a constant pressure drop funnel, nitrogen inlet and mechanical stirring, and heating to 60℃. 20g C₁₈H₃₇- (OC₃H₆) ₁₅-OH was dropped into the MDI prepolymer for 30 minutes, and reacted for further 20 minutes at 60℃ to prepare the Inventive MDI-based prepolymer binder Example 6 (IE6) . The prepared Inventive MDI-based prepolymer binder Example 6 was cooled down and poured into a plastic container for storage. The whole process was operated under nitrogen atmosphere.

Comparative Example 1 (CE1)

100g VORAMER^TM MR 1045K isocyanate (MDI prepolymer) .

Table 2 Formulations of Inventive Examples 1-6 and Comparative Example 1

IV. Results

IE1 and IE2 both used C₁₈H₃₇- (OC₃H₆) ₈-OH, but the preparation procedure is different. By using C₁₈H₃₇- (OC₃H₆) ₈-OH, the tack free time of the prepared MDI-based prepolymer binder was significantly extended from 2.5 hours to 5-5.5 hours compared with MDI prepolymer (CE1) . By continuously increasing the content of C₁₈H₃₇- (OC₃H₆) ₈-OH from 14.25％ (IE1 and IE2) to 19％ (IE3) in the whole formulation, while an improved tack free time compared to CE1 is realized, a decreasing trend in tensile strength is also observed.

IE4, IE5 and IE6 used C₁₈H₃₇- (OC₃H₆) ₁₅-OH with different contents. Compared to that of MDI prepolymer (CE1) , MDI-based prepolymer binders (IE4-6) significantly extended their tack free times. Furthermore, the addition of aliphatic isocyanate crosslinker, DESMODUR^TM N 3300A crosslinker, helps improve both the tensile strength and elongation at break values.

Claims

A novel MDI-based prepolymer binder which is a reaction product of an MDI prepolymer, or a mixture of an MDI prepolymer and an MDI monomer, with a compound having the following Formula (I) or Formula (II) :

wherein R₁, R₂ and R₃ may be identical, or different, and are each individually selected from H, and C_aH_b, wherein a is an integral of from 1 to 40, and b is an integral of from 2a-4 to 2a+1, wherein R₁, R₂, and R₃ are not all H；

and R is represented by (OC_mH_2m) _n, wherein m is an integral from 2 to 5, and n is an integral from 3 to 40.
The novel MDI-based prepolymer binder according to Claim 1 wherein the MDI monomer is 4, 4-MDI, 2, 4-MDI, or the mixture thereof.
The novel MDI-based prepolymer binder according to Claim 1 wherein the MDI prepolymer is a reaction product of a polyol with excessive MDI monomer, and has an isocyanate content of from 5％to 25％.
The novel MDI-based prepolymer binder according to Claim 1 wherein the compound of Formula (I) or Formula (II) is from 5 to 40wt％, based on total weight of the MDI-based prepolymer binder.
The novel MDI-based prepolymer binder according to Claim 1 further comprises from 0.5 to 10wt％, based on total weight of the MDI-based prepolymer binder, an aliphatic isocyanate crosslinker.
The novel MDI-based prepolymer binder according to Claim 5 wherein the aliphatic isocyanate crosslinker has an NCO functionality equal to or above 3.
The novel MDI-based prepolymer binder, wherein the MDI-based prepolymer binder is a sports covering, playground covering, or racing tracking.
An elastomeric composite that is the mixing product of the MDI-based prepolymer binder according to Claim 1 with particles of a natural or synthetic rubber.
An elastomeric composite formed by mixing the MDI-based prepolymer binder according to Claim 1 and particles of a natural or synthetic rubber, and curing the MDI-based prepolymer binder.