Phloroglucinol resins, methods of manufacture, and uses in rubber compositions

Abstract

The solid phloroglucinol resin comprises reacting a phloroglucinol compound with a ketone in the presence of an acid catalyst, and the solid phloroglucinol resin formed comprises a plurality of phloroglucinol units defined by formula (I). [Formula 1] TIFF2023510303000016.tif51161 wherein at least one of R1, R2 and R3 is bonded to a second phloroglucinol unit to form a disubstituted methylene bridge, and the second of R1, R2 and R3 is a hydrogen atom, or is bonded to a third phloroglucinol unit to form another disubstituted methylene bridge, and the third of R1, R2 and R3 is a hydrogen atom.

Description

[Technical field]

[0001] FIELD OF THEINVENTION This invention relates to solid phloroglucinol resins and methods for making same. Such solid phloroglucinol resins may be useful in vulcanizable rubber compositions. [Background technology]

[0002] Resorcinol-formaldehyde resins, also called RF resins or resorcinol resins, formed as the reaction product of resorcinol and formaldehyde, are widely used in various applications including rubber compounding. In the preparation of rubber compounds, solid RF resins have long been used to enhance rubber properties such as adhesion properties between rubber and reinforcing materials and dynamic properties of articles such as tires, belts and hose products.

[0003] Resorcinol resins generally have 10-20% unreacted or free resorcinol. The amount of free resorcinol can be an important factor in balancing important properties. However, the presence of free resorcinol can be problematic. For example, free resorcinol can volatilize during rubber mixing, and such volatilization is often referred to as fuming, thereby causing additional problems in the rubber mixing process. Additionally, the presence of free resorcinol contributes to the hygroscopic nature of resorcinol resins, which creates storage and handling problems.

[0004] Formaldehyde has been used to manufacture resorcinol-formaldehyde resins for many years. Given its widespread use, toxicity, and volatility, formaldehyde presents potential health and environmental concerns. In 2011, the US National Toxicology Program described formaldehyde as a known human carcinogen.

[0005] Therefore, there is a need to create an environmentally friendly adhesive that does not use resorcinol and formaldehyde (or other aldehydes). Unfortunately, all prior art adhesive resins known so far that do not contain resorcinol and formaldehyde have generally been found to have low reactivity, which leads to poor rubber performance and / or processing problems. For example, the softening point of the resin may be adversely affected, making it difficult to use and process. That is, if the softening point is too high, it will be difficult to mix with the rubber compound, while if the softening point is too low, handling problems will occur. Therefore, it is necessary to balance the competing factors of reactivity and softening point.

[0006] The use of phloroglucinol in aqueous adhesive compositions is well known in the art. For example, US Patent Application Publication No. 2014 / 0235125 describes an aqueous adhesive composition comprising a phenol / aldehyde resin and an unsaturated elastomer latex. The phenol / aldehyde resin is based on at least an aromatic polyaldehyde having at least two aldehyde functional groups and containing at least one aromatic nucleus, and phloroglucinol.

[0007] In US 2019 / 0119535, the aqueous adhesive composition includes a thermosetting resin and an unsaturated elastomer latex. The thermosetting resin may include an aromatic compound having at least two functional groups, one hydroxymethyl functional group and the other aldehyde or hydroxymethyl functional group. Generally, phloroglucinol is disclosed in both references, but both compositions are aqueous (not solid) and preferably contain an aldehyde (not ketone). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Application Publication No. 2014 / 0235125 [Patent Document 2] US Patent Application Publication No. 2019 / 0119535 Summary of the Invention

[0009] At least one aspect of the present invention provides a solid phloroglucinol resin comprising a reaction product of a phloroglucinol compound, preferably phloroglucinol, and a ketone. In various embodiments, the ketone may be selected from the group consisting of acetone, methyl ethyl ketone, diethyl ketone, ethyl butyl ketone, diisobutyl ketone, methyl isopropyl ketone, diisopropyl ketone, and methyl isobutyl ketone. In other embodiments, the ketone may be selected from the group consisting of acetone, methyl ethyl ketone, and methyl isobutyl ketone. In at least one embodiment, the ketone is acetone. In another embodiment, the ketone is methyl ethyl ketone. In yet another embodiment, the ketone is methyl isobutyl ketone.

[0010] To produce the solid phloroglucinol resin, the phloroglucinol compound is reacted with a ketone in the presence of an acid catalyst. In at least one embodiment, the acid catalyst is selected from an inorganic acid, an acidic cation exchange resin, and combinations thereof. In at least one embodiment, the inorganic acid is thioglycolic acid. In at least another embodiment, the acidic cation exchange resin comprises sulfuric acid or hydrochloric acid.

[0011] Yet another aspect of the present invention provides a vulcanizable rubber composition comprising a vulcanizable rubber, a curing agent, and a solid phloroglucinol resin comprising a reaction product of a phloroglucinol compound and a ketone. Advantageously, it will be appreciated that the vulcanized rubber composition of the present invention exhibits advantageous rubber properties, such as adhesion, hardness, and dynamic properties, without affecting the cure time during vulcanization, as compared to conventional products.

[0012] In general, it will be appreciated that the present invention provides a solid phloroglucinol resin comprising a plurality of phloroglucinol units as defined by formula (I). [ka] wherein at least one of R1, R2 and R3 is linked to a second phloroglucinol unit to form a disubstituted methylene bridge, and the second of R1, R2 and R3 is a hydrogen atom, or linked to a third phloroglucinol unit to form another disubstituted methylene bridge, and the third of R1, R2 and R3 is a hydrogen atom.

[0013] More particularly, the present invention also provides the above solid phloroglucinol resin further defined by formula (II): [ka] wherein n is an integer from 1 to 20, R1 in the first phloroglucinol unit on the left is substituted at the 2-position with a disubstituted methylene bridge, and R3 in the second phloroglucinol unit on the right is substituted at the 6-position with the same disubstituted methylene bridge, wherein R3 on the first phloroglucinol unit on the left and R1 on the second phloroglucinol unit on the right form separate disubstituted methylene bridges or can be hydrogen atoms, R2 is a hydrogen atom, and wherein R4 and R5 can be the same or different and are alkyl groups.

[0014] In some embodiments based on the above resins, the solid phloroglucinol resin may have R4 and R5 both being methyl groups, and the disubstituted methylene bridge formed is an isopropylidene bridge. In other embodiments based on the above resins, R4 may be an ethyl group, R5 may be a methyl group, and the disubstituted methylene bridge formed is a 2,2-disubstituted butane bridge. In yet other embodiments based on the above resins, R4 may be an isopropyl group, R5 may be a methyl group, and the disubstituted methylene bridge formed is a 2,2-disubstituted 4-methylpentane bridge.

[0015] Yet another aspect of the present invention is to provide a solid phloroglucinol resin comprising the reaction product of phloroglucinol and a ketone in the presence of an acid catalyst. For such resins, the ketone may be selected from the group consisting of acetone, methyl ethyl ketone (MEK), diethyl ketone, ethyl butyl ketone, diisobutyl ketone, methyl isopropyl ketone, diisopropyl ketone, and methyl isobutyl ketone (MIBK). In some embodiments, the ketone may be selected from the group consisting of acetone, methyl ethyl ketone, and methyl isobutyl ketone. In some embodiments, the acid catalyst is selected from the group consisting of inorganic acids and acidic cation exchange resins.

[0016] In one or more embodiments based on the above resins, the molar ratio of ketone to phloroglucinol may be greater than 1:1 and less than 20:1. In one or more embodiments based on the above resins, the resin may contain less than 40% by weight of unreacted phloroglucinol. In one or more embodiments based on the above resins, the resin may have a weight average molecular weight (Mw) greater than 400 g / mol and less than 700 g / mol. In one or more embodiments based on the above resins, the resin may have a softening point greater than 80° C. In one or more embodiments based on the above resins, the resin may contain less than 1.5% by weight of water. In one or more embodiments based on the above resins, the resin may have a pentamer or higher oligomer content less than 55% according to GPC using polystyrene standards.

[0017] Yet another aspect of the present invention is to provide a vulcanizable rubber composition comprising a vulcanizable rubber, a curing agent, and a solid phloroglucinol resin as described above. In yet another aspect, a vulcanized rubber prepared from the vulcanizable composition described above may be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention is based, at least in part, on the discovery of solid phloroglucinol resins that can replace solid RF resins when incorporated into vulcanizable rubber compositions. Such solid phloroglucinol resins do not use aldehydes such as resorcinol or formaldehyde. Instead, solid phloroglucinol resins contain a plurality of phloroglucinol units generally defined by formula (I): [ka] wherein at least one of R1, R2 and R3 is bonded to a second phloroglucinol unit to form a disubstituted methylene bridge, the second of R1, R2 and R3 being a hydrogen atom, or is bonded to a third phloroglucinol unit to form another disubstituted methylene bridge, the third of R1, R2 and R3 being a hydrogen atom. The structure used in formula (I) is intended to represent the fact that the disubstituted methylene bridge(s) of R1, R2 or R3 can be bonded to the 2-, 4- or 6-position on the aromatic ring. Also, the hydrogen atom of R1, R2 or R3 is located at the 2-, 4- or 6-position. Those skilled in the art will understand that any carbon atom in the aromatic ring that is not bonded to a hydroxyl group can be bonded to R1, R2 or R3 and includes a hydrogen atom or is part of a disubstituted methylene bridge.

[0019] Typically, the disubstituted methylene bridge comprises a methylene bridge having at least two C1-C10 alkyl groups extending therefrom. In another embodiment, the methylene bridge comprises at least two C1-C5 alkyl groups extending therefrom. In yet another embodiment, the methylene bridge comprises at least two C1-C4 alkyl groups extending therefrom. In yet another embodiment, the methylene bridge comprises at least two C1-C3 alkyl groups extending therefrom. In yet yet another embodiment, the methylene bridge comprises at least two C1-C2 alkyl groups extending therefrom.

[0020] More specifically, the phloroglucinol resin of the present invention can be described as shown in formula (II): [ka] where n is an integer between 1 and 20, R1 in the phloroglucinol unit on the left is substituted at the 2-position with a disubstituted methylene bridge as shown, and R3 in the phloroglucinol unit on the right is substituted at the 6-position. R3 on the left and R1 on the right may also be the same disubstituted methylene bridges as shown herein or may be hydrogen atoms, and R2 may be a hydrogen atom in this embodiment shown. R4 and R5 may be the same or different and are alkyl groups. In one embodiment, R4 and R5 may both be methyl groups, and the disubstituted methylene bridge formed is an isopropyldene bridge. In another embodiment, R4 may be an ethyl group, R5 may be a methyl group, and the disubstituted methylene bridge formed is a 2,2-disubstituted butane bridge. In yet another embodiment, R4 may be an isopropyl group, R5 may be a methyl group, and the disubstituted methylene bridge formed is a 2,2-disubstituted 4-methylpentane bridge. In some embodiments, n is an integer from 1-8; in other embodiments, n is an integer from 1-5.

[0021] As alluded to above, aspects of the present invention benefit from the solid nature of the phloroglucinol resin. Thus, the phloroglucinol resin of the present invention can be characterized by the absence or limited amount of water present within the phloroglucinol resin. In one or more embodiments, the solid phloroglucinol resin of the present invention contains less than 3% by weight, in other embodiments less than 2% by weight, in other embodiments less than 1% by weight, in other embodiments less than 0.5% by weight, in other embodiments less than 0.25% by weight, in other embodiments less than 0.10% by weight of water based on the total weight of the solid resin. In one or more embodiments, the phloroglucinol resin of the present invention is substantially free of water, which refers to an amount of water at or below that would otherwise appreciably affect the resin or its use. In certain embodiments, the phloroglucinol resin of the present invention is free of water. As one of ordinary skill in the art will appreciate, the amount of water in the resin can be determined by a variety of methods, including, but not limited to, Karl Fischer titration. In a particular embodiment, the amount of water is determined using a modified version of ASTM E 203, where the method is modified by replacing the injection septum with a stopper, and the grind resin is added through this port.

[0022] The solid phloroglucinol resin of the present invention is characterized by a low molecular weight. As those skilled in the art will appreciate, the molecular weight of a phloroglucinol resin can be determined using a number of methods, and the molecular weight is typically reported in terms of weight average molecular weight (Mw) or number average molecular weight (Mn). Useful techniques for determining the molecular weight of a solid phloroglucinol resin include gel permeation chromatography using polystyrene standards (GPC) or gas phase osmometry.

[0023] In one or more embodiments, the solid phloroglucinol resin composition of the present invention may be characterized by a weight average molecular weight (Mw), which may be determined by GPC using polystyrene standards. In one or more embodiments, the Mw of the resin is greater than 270 g / mol, in other embodiments greater than 290 g / mol, in other embodiments greater than 310 g / mol, in other embodiments greater than 350 g / mol, and in other embodiments greater than 400 g / mol. In these or other embodiments, the Mw of the resin is less than 900 g / mol, in other embodiments less than 800 g / mol, and in other embodiments less than 700 g / mol. In these or other embodiments, the solid phloroglucinol resin of the present invention may be characterized by a Mw of about 270 to about 900 g / mol, in other embodiments from about 310 to about 900 g / mol, in other embodiments from about 350 to about 800 g / mol, and in other embodiments from about 400 to about 700 g / mol.

[0024] In one or more embodiments, the solid phloroglucinol resin compositions of the present invention may be characterized by a softening point of greater than 90° C., greater than 100° C. in other embodiments, greater than 110° C. in other embodiments, greater than 120° C. in other embodiments, greater than 130° C. in other embodiments, greater than 140° C. in other embodiments, greater than 160° C. in other embodiments, and greater than 180° C. In these or other embodiments, the solid phloroglucinol resins of the present invention may be characterized by a softening point of from about 80° C. to about 180° C., from about 95° C. to about 140° C. in other embodiments, and from about 100° C. to about 130° C. in other embodiments. The softening point of the resin may be determined according to the following method, with reference to the latest editions of ASTM E 28 and ASTM D 6090, which are incorporated herein by reference in their entireties. The method may use a Mettler softening point apparatus, which may include a control unit model FP-90 or equivalent, a furnace model FP-83 or equivalent, and a cartridge assembly, a timer, a porcelain evaporating dish (approximately 3 inches (7.62 cm) in diameter), and a hot plate. The method may use a pitch-type cup drilled to a 0.257 inch (1.958 cm) opening (F drill), and a 440 stainless steel ball (0.2500 inch (0.4896 cm) in diameter, which must pass through the cup). The apparatus may be calibrated according to ASTM D 6090. The resin sample (approximately 15 grams) may be melted in a porcelain or aluminum evaporating dish on the surface of a hot plate at 600-650°F (316-343°C) for approximately 4 minutes. After melting, the sample may be poured into a cup that has been preheated to at least the temperature of the molten resin. The amount of resin sample poured into the cup should be such that after solidification, the excess can be removed with a heated spatula or putty knife. The sample is then cooled to room temperature in a desiccator, and then the cartridge can be assembled so that the ball rests on top of the resin. The assembled cartridge is then placed in an oven, which can be preset to 85°C or 10-15°C below the expected softening point. The heating rate can be set at 1°C / min. The cartridge can then be rotated until it is locked into place.After 30 seconds, the softening point apparatus can be started and the softening point measurement completed.

[0025] Depending on the ketone used with the phloroglucinol compound, a crosslinked structure similar to the methylene bridged structure exhibited by known RF resins is developed. More specifically, when a ketone is combined with a phloroglucinol compound such as phloroglucinol, a solid phloroglucinol resin having a disubstituted methylene bridged structure and a relatively low molecular weight is produced. Importantly, this new phloroglucinol resin does not use resorcinol or formaldehyde.

[0026] More specifically, in one or more embodiments, the phloroglucinol resin of the present invention is generally prepared by reacting a phloroglucinol compound with a ketone in the presence of an acid catalyst. That is, the phloroglucinol resin comprises the reaction product of phloroglucinol and a ketone in the presence of an acid catalyst. As those skilled in the art will recognize, as described above, phloroglucinol compounds include, but are not limited to, phloroglucinol, also known as trihydric phenol or 1,3,5-dihydroxybenzene, or free phloroglucinol. The chemical formula of phloroglucinol is shown below in formula (III). [ka]

[0027] The molar ratio of ketone to phloroglucinol may vary from 1:1 to 20:1. In some other embodiments, the molar ratio may vary from greater than 1:1 to less than 20:1. In other embodiments, the molar ratio may vary from 1.5:1 to 16:1, and in other embodiments, the molar ratio may vary from greater than 1.5:1 to less than 15:1. In still other embodiments, the molar ratio may vary from 2:1 to 16:1, and in other embodiments, the molar ratio may vary from greater than 2:1 to less than 15:1. In still other embodiments, the molar ratio of ketone to phloroglucinol may vary from about 1.5:1 to about 10:1, in other embodiments from about 1.5:1 to about 8:1, and in still other embodiments, from about 2:1 to about 6:1.

[0028] In one or more embodiments, the ketone may be selected from the group consisting of acetone, methyl ethyl ketone, diethyl ketone, ethyl butyl ketone, diisobutyl ketone, methyl isopropyl ketone, diisopropyl ketone, and methyl isobutyl ketone. In certain embodiments, the ketone is acetone. In other embodiments, the ketone is methyl ethyl ketone, and in yet other embodiments, the ketone is methyl isobutyl ketone.

[0029] The condensation reaction of phloroglucinol with ketones may be carried out in the presence of a catalyst. Useful catalysts include conventional acid catalysts. Examples of suitable acid catalysts include inorganic acids such as phosphoric acid, hydrochloric acid, and sulfuric acid, and acidic ion exchange resins such as acidic cation exchange resins. Other catalysts can be used as well. Such catalysts include inorganic acid catalysts such as thioglycolic acid.

[0030] According to an aspect of the present invention, the reaction of phloroglucinol (or a phloroglucinol compound) with a ketone is carried out in the presence of an organic solvent. Examples of suitable organic solvents include polar and non-polar solvents. In one or more embodiments, the solvent may be selected from acetone, methyl isobutyl ketone (MIBK), methyl tert-butyl ether, cyclopentyl methyl ether, ethyl acetate, methanol, ethanol, isopropanol, n-propanol, acetonitrile, dimethylsulfoxide, dimethylformamide, and tetrahydrofuran, chlorobenzene, dichlorobenzene, pentane, hexane, toluene, and xylene. In one embodiment, acetone and toluene are preferably used.

[0031] In one or more embodiments, the reaction (resin formation) may be carried out at a temperature range of 10 to 150° C., and in other embodiments, at a temperature range of about 25 to about 130° C. In one embodiment, the reaction temperature is greater than 30° C., in another embodiment, the reaction temperature is greater than 40° C., in another embodiment, the reaction temperature is greater than 50° C., and in another embodiment, the reaction temperature is greater than 60° C.

[0032] In one or more embodiments, the reaction of the phloroglucinol compound with the aldehyde or ketone is carried out in the presence of a threshold amount of organic solvent. Specifically, the amount or organic solvent present in the reaction can be described with reference to the amount of phloroglucinol charged to the reaction (i.e., in the initial mixture). In one or more embodiments, the initial mixture in which the reaction occurs contains more than 30 parts by weight, in other embodiments more than 50 parts by weight, and in other embodiments more than 70 parts by weight of organic solvent per 100 parts by weight of phloroglucinol. In these or other embodiments, the mixture in which the reaction occurs (before the addition of the aldehyde) contains less than 500 parts by weight, in other embodiments less than 400 parts by weight, and in other embodiments less than 300 parts by weight of organic solvent per 100 parts by weight of resorcinol. In one or more embodiments, the mixture in which the reaction occurs contains from about 30 to about 500, in other embodiments from about 50 to about 400, and in other embodiments from about 70 to about 300 parts by weight of organic solvent per 100 parts by weight of resorcinol.

[0033] One skilled in the art can easily determine the appropriate level of acid catalyst to be used. The amount of acid catalyst introduced into the mixture is described with reference to the amount of phloroglucinol initially present. In one or more embodiments, the initial mixture in which the reaction occurs contains more than 0.1 parts by weight, in other embodiments more than 0.2 parts by weight, in other embodiments more than 0.5 parts by weight, in other embodiments more than 1 part by weight, in other embodiments more than 2 parts by weight, and in other embodiments more than 5 parts by weight of inorganic catalyst per 100 parts by weight of phloroglucinol. In these or other embodiments, the mixture in which the reaction occurs contains less than 50 parts by weight, in other embodiments less than 40 parts by weight, and in other embodiments less than 30 parts by weight of inorganic catalyst per 100 parts by weight of phloroglucinol. In one or more embodiments, the mixture in which the reaction occurs contains from about 0.1 to about 50 parts by weight, in other embodiments from about 1 to about 40 parts by weight, and in other embodiments from about 5 to about 30 parts by weight of inorganic catalyst per 100 parts by weight of phloroglucinol.

[0034] In one or more embodiments, the initial mixture in which the reaction occurs contains greater than 10 parts by weight, greater than 25 parts by weight in other embodiments, and greater than 50 parts by weight in other embodiments, of the acidic cation exchange catalyst per 100 parts by weight of phloroglucinol. In these or other embodiments, the mixture in which the reaction occurs contains less than 500 parts by weight, less than 400 parts by weight in other embodiments, and less than 200 parts by weight of the inorganic catalyst per 100 parts by weight of phloroglucinol. In one or more embodiments, the mixture in which the reaction occurs contains from about 10 to about 500 parts by weight, from about 25 to about 400 parts by weight in other embodiments, and from about 50 to about 200 parts by weight of the acidic cation exchange catalyst per 100 parts by weight of phloroglucinol.

[0035] Those skilled in the art can easily determine the appropriate level of any thiol or sulfide to be used as a cocatalyst with the acid catalyst in the reaction. The cocatalyst enhances the reaction rate by using the acid catalyst and the phloroglucinol compound together. In one or more embodiments, the cocatalyst can be selected from the group consisting of sodium sulfate, sodium thiosulfate, sodium bisulfite, mercaptoethanol, sodium dithionite, thioglycolic acid, sodium sulfide, and ethanethiol. In certain embodiments, the cocatalyst is thioglycolic acid.

[0036] The amount of cocatalyst introduced into the mixture is described with reference to the amount of phloroglucinol initially present. In one or more embodiments, the initial mixture in which the reaction occurs contains greater than 0.01 parts by weight, greater than 0.5 parts by weight in other embodiments, and greater than 1 part by weight in other embodiments, of inorganic catalyst per 100 parts by weight of phloroglucinol. In these or other embodiments, the mixture in which the reaction occurs contains less than 30 parts by weight, less than 20 parts by weight in other embodiments, and less than 10 parts by weight in other embodiments, of inorganic catalyst per 100 parts by weight of phloroglucinol. In one or more embodiments, the mixture in which the reaction occurs contains from about 0.01 to about 30, from about 0.5 to about 20, and from about 1 to about 10 parts by weight in other embodiments, of inorganic catalyst per 100 parts by weight of phloroglucinol.

[0037] Turning now to the preparation of a particular phloroglucinol resin, it will be appreciated that combining acetone with a phloroglucinol compound, such as phloroglucinol, produces a phloroglucinol resin having an isopropyldene bridge structure and a relatively low molecular weight. The reaction is shown in more detail in Scheme I below. [ka] It will be understood that each isopropylidene bridge structure is a disubstituted methylene bridge having a methyl group as a substituent.

[0038] Similarly, when methyl ethyl ketone is used in combination with a phloroglucinol compound such as phloroglucinol, a phloroglucinol resin having a 2,2-disubstituted butane bridge structure is produced. The reaction is shown in more detail in Scheme II below. [ka] It will be understood that each 2,2-disubstituted butane bridge structure is a disubstituted methylene bridge having one methyl group and one ethyl group extending from the methylene bridge as substituents.

[0039] Additionally, methyl isobutyl ketone can be used in combination with a phloroglucinol compound such as phloroglucinol to produce a phloroglucinol resin having a 2,2-isopropyl, 4-methylpentane bridge structure. The reaction is shown in more detail in Scheme III below. [ka] It will be understood that each 2,2-disubstituted 4-methylpentane bridge structure is a disubstituted methylene bridge having one methyl group and one isopropyl group extending from the methylene bridge as substituents.

[0040] Upon removal of the solvent, the resulting product is a solid phloroglucinol resin. Importantly, when incorporated into vulcanizable rubber compositions, these solid phloroglucinol resins have been found to produce unexpected results including, among other things, improved physical properties of the cured rubber (e.g., Shore A hardness) and dynamic properties of the cured rubber (e.g., higher G'), and to have suitable processing characteristics, such as sufficient cure times, not previously seen with resorcinol-free alternative resins.

[0041] As alluded to above, the phloroglucinol resins of the present invention are useful in vulcanizable rubber compositions. In addition to using the phloroglucinol resins of the present invention, the vulcanizable compositions can otherwise be conventional in nature. Thus, the rubber composition may include a vulcanizable rubber, a curing agent, a filler, and the phloroglucinol resins of the present invention.

[0042] With regard to the rubber composition of the present invention, the rubber composition may include a rubber component which may include any natural rubber, synthetic rubber, or a combination thereof. Examples of synthetic rubbers include, but are not limited to, styrene butadiene copolymers, polyisoprene, polybutadiene, acrylonitrile butadiene styrene, polychloroprene, polyisobutylene, ethylene-propylene copolymers, and ethylene-propylene-diene rubber.

[0043] The rubber composition may also include one or more of the conventional additives used in such compositions, examples of such additives include carbon black, cobalt salts, stearic acid, silica, silicic acid, sulfur, peroxides, zinc oxide, fillers, antioxidants, and softening oils.

[0044] Aspects of the invention relate to the amount or loading of the solid phloroglucinol resin of the invention in the vulcanizable composition. In one or more embodiments, the vulcanizable composition of the invention comprises greater than 0.5 parts by weight, in other embodiments greater than 1.0 parts by weight, in other embodiments greater than 1.5 parts by weight, and in other embodiments greater than 2.0 parts by weight of the solid phloroglucinol resin per 100 parts by weight of rubber. In these or other embodiments, the vulcanizable composition of the invention comprises less than 7.0 parts by weight, in other embodiments less than 6.0 parts by weight, in other embodiments less than 5.0 parts by weight, and in other embodiments less than 4.0 parts by weight of the solid phloroglucinol resin per 100 parts by weight of rubber. In one or more embodiments, the vulcanizable composition of the invention comprises from about 0.5 to about 7.0 parts by weight, in other embodiments from about 1.0 to about 6.0 parts by weight, in other embodiments from about 1.5 to about 5.0 parts by weight, and in other embodiments from about 2.0 to about 4.5 parts by weight of the phloroglucinol resin per 100 parts by weight of rubber.

[0045] The rubber composition may also include one or more methylene donor components. The methylene donor component is any compound that produces formaldehyde upon heating during vulcanization. Examples of such compounds are described in U.S. Pat. No. 3,751,331, which is incorporated herein by reference. Preferred methylene donor compounds are hexamethylenetetramine, di-methylolmelamine, tri-methylolmelamine, tetra-methylolmelamine, penta-methylolmelamine, hexa-methylolmelamine, and mixtures thereof. The methylolmelamine may be fully or partially etherified or esterified, such as hexamethoxymethylolmelamine. The methylene donor may be present in a concentration of about 0.1 to 15 parts per hundred parts of rubber, or in other embodiments, 0.1 to 10 parts per hundred parts of rubber. The ratio of methylene donor to solid phloroglucinol resin may be 1:10 to 10:1.

[0046] As will be appreciated, the rubber components, additives, reinforcing materials, and methylene donor compounds are known, as are methods of vulcanizing the compositions. The improvement of the present invention relates to solid phloroglucinol resins.

[0047] The rubber composition is prepared and used in the conventional manner for preparing and using such compositions, that is, the composition may be prepared by solid mixing.

[0048] In light of the above, it will be understood that the rubber compositions produced according to the present invention can be used in various rubber applications or rubber products. The uncured and cured rubber compositions of the present invention may be used in tire applications or may be used to prepare parts of tires, such as tire treads, belt skimstocks, sidewalls, bead compounds, carcasses, or other areas of tires. Other applications include rubber products useful for engine mounts and bushings. Still other examples of applications in which the uncured and cured rubber compositions of the present invention can be used or prepared include technical or mechanical rubber products, such as hoses, pneumatic belts, and conveyor belts. EXAMPLES

[0049] In order to demonstrate the practice of the present invention, the following examples have been prepared and tested. However, the examples should not be construed as limiting the scope of the invention. The claims serve to define the invention. The abbreviation PG means "phloroglucinol".

[0050] PG resin example 1. 25.2 g of phloroglucinol, 47.0 g of acetone, 50.4 g of toluene, 1.1 g of thioglycolic acid, and 1.2 g of 98% sulfuric acid were placed in a flask and heated to 80° C. The reaction mixture was maintained at about 80° C. for 9 hours. 3.8 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0051] PG resin example 2. 30.3 g of phloroglucinol, 69.7 g of acetone, 1.3 g of thioglycolic acid, and 20.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 70° C. The reaction mixture was maintained at about 70° C. for 22 hours. 0.8 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0052] PG resin example 3. 25.2 g of phloroglucinol, 24.4 g of acetone, 63.1 g of toluene, 1.1 g of thioglycolic acid, and 20.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 82° C. The reaction mixture was maintained at about 82° C. for 22 hours. 1.2 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0053] PG resin example 4. 80.0 g of phloroglucinol, 114.3 g of acetone and 63.5 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 70° C. The reaction mixture was maintained at about 70° C. for 24 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0054] PG resin example 5. 80.0 g of phloroglucinol, 114.3 g of acetone and 63.5 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 70° C. The reaction mixture was maintained at about 70° C. for 5 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0055] PG resin example 6. 25.2 g of phloroglucinol, 44.7 g of methyl ethyl ketone and 20.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 80° C. The reaction mixture was maintained at about 80° C. for 24 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0056] PG resin example 7. 50.0 g of phloroglucinol, 72.6 g of methyl ethyl ketone and 40.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 85° C. The reaction mixture was maintained at about 85° C. for 24 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0057] PG resin example 8. 50.0 g of phloroglucinol, 57.0 g of methyl ethyl ketone and 40.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 85° C. The reaction mixture was maintained at about 85° C. for 24 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0058] PG resin example 9. 25.2 g of phloroglucinol, 61.2 g of methyl isobutyl ketone and 20.0 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were placed in a flask and heated to 117° C. The reaction mixture was maintained at about 117° C. for 22 hours. 0.1 g of sodium hydroxide (25% solution) was then added. The solvent was then removed by vacuum distillation to 155° C. Once a temperature of 155° C. was reached, the vacuum was released and the resin was drained from the flask.

[0059] Table 1 below provides a general description of the components used in the formation of phloroglucinol resins. It will be understood that in these examples, either sulfuric acid (H2SO4) or a cation exchange catalyst was used as the acid catalyst, and some of the examples further used a co-catalyst such as thioglycolic acid.

[0060] [Table 1]

[0061] It should be understood that in order to provide a complete analysis of the improvements provided by the above uniquely prepared solid phloroglucinol resins, a resorcinol formaldehyde resin available from Sumitomo Chemical under the trade name PENACOLITE® RESIN B-19-SC was provided as a comparative RF resin. Thus, rubber compounds containing the phloroglucinol resins described in the Examples and Table 1, as well as the comparative RF resins also provided in Table 1, were prepared according to the rubber compositions shown in Table 2.

[0062] [Table 2]

[0063] Rubber compositions containing each of the five phloroglucinol resins were then tested against a rubber composition containing a comparative RF resin (Example 6 - Comparative) also shown in Table 1. The rubber compositions were then tested for essentially the same properties and rubber performance characteristics.

[0064] Various physical properties and chemical analysis of the solid phloroglucinol resin are provided in Table 3 below. In evaluating the resin properties, it will be appreciated that the softening point of the resin was determined using the procedure described above, and the molecular weight and oligomer distribution were determined by GPC analysis. The resulting rubber performance based on the preparation of the vulcanized rubber shown below is also shown in Table 3. It will be appreciated that T'90 was measured at 150°C, 0.5°arc and 1.6Hz using an Alpha Technologies MDR rheometer (MDR 2000) according to ASTM D-5289. The rubber compound was cured at 150°C and 10 tons of pressure according to the parameters obtained from the MDR 2000 rheometry test data. G' and tan δ, which are indicators of compound hysteresis or heat build-up, were measured at 2.0% torsional shear strain at 1Hz and 60°C using a TA Instruments rheometer (ARES), and Shore A hardness was measured according to ASTM D-2240. The undegraded pull-out force and humidity aging (21 days, 85° C. / 90 RH) were measured according to ASTM D-2229.

[0065] [Table 3] TIFF0007618679000012.tif105167

[0066] In comparing the phloroglucinol resins of the present invention with those of the comparative examples, it can be seen that the phloroglucinol resins of the present invention improve the mechanical properties of the cured rubber compounds and provide better adhesive properties compared to conventional resorcinol formaldehyde resins.

[0067] Additionally, the phloroglucinol resins of the present invention have a significantly narrower range of Mw than the comparative examples, where Mw is greater than 400 g / mol and less than 700 g / mol, whereas the comparative examples have Mw greater than 700 g / mol.

[0068] Various modifications and alterations that do not depart from the scope and spirit of this invention will become apparent to those skilled in the art. The present invention should not be limited in any precise manner to the illustrative embodiments set forth herein.

Claims

1. A solid phloroglucinol resin comprising the reaction product of phloroglucinol and a ketone in the presence of an acid catalyst, the solid phloroglucinol resin comprising at least one phloroglucinol unit defined by formula (II): 【Chemistry 2】 wherein n is an integer from 1 to 20; R1 and R3, which may be the same or different, each form a disubstituted methylene bridge or are a hydrogen atom; R2 is a hydrogen atom; and R4 and R5, which may be the same or different, are alkyl groups.

2. 2. The solid phloroglucinol resin of claim 1, wherein R4 and R5 are both methyl groups and the disubstituted methylene bridge formed is an isopropyldene bridge.

3. 2. The solid phloroglucinol resin of claim 1, wherein R4 is an ethyl group, R5 is a methyl group, and the formed disubstituted methylene bridge is a 2,2-disubstituted butane bridge.

4. 2. The solid phloroglucinol resin of claim 1, wherein R4 is an isopropyl group, R5 is a methyl group, and the formed disubstituted methylene bridge is a 2,2-disubstituted 4-methylpentane bridge.

5. 2. The solid phloroglucinol resin of claim 1, wherein the ketone is selected from the group consisting of acetone, methyl ethyl ketone (MEK), diethyl ketone, ethyl butyl ketone, diisobutyl ketone, methyl isopropyl ketone, diisopropyl ketone, and methyl isobutyl ketone (MIBK).

6. 6. The solid phloroglucinol resin of claim 5, wherein the ketone is selected from the group consisting of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

7. 2. The solid phloroglucinol resin of claim 1, wherein the acid catalyst is an inorganic acid.

8. The solid phloroglucinol resin of claim 1, wherein the acid catalyst is an acidic cation exchange resin.

9. 2. The solid phloroglucinol resin of claim 1, wherein the molar ratio of ketone to phloroglucinol is greater than 1:1 and less than 20:

1.

10. 10. The solid phloroglucinol resin according to any one of claims 1 to 9, containing less than 40% by weight of unreacted phloroglucinol.

11. 11. The solid phloroglucinol resin according to any one of claims 1 to 10, having a Mw greater than 400 g / mol and less than 700 g / mol.

12. The solid phloroglucinol resin according to any one of claims 1 to 11, having a softening point of more than 80°C.

13. The solid phloroglucinol resin according to any one of claims 1 to 12, containing less than 1.5% by weight of water.

14. The solid phloroglucinol resin according to any one of claims 1 to 13, having a pentamer or higher oligomer content of less than 55% by GPC using a polystyrene standard.

15. a. vulcanizable rubber; b. a hardener; and c) The solid phloroglucinol resin according to any one of claims 1 to 14.

1. A vulcanizable rubber composition comprising:

16. A vulcanized rubber prepared from the vulcanizable composition of claim 15.

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