Phenolic tackifiers

Specific interactions in binary blends of ethylene-vinyl acetate copolymer with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron acceptor ability of the resin, by using attenuated total reflection FTIR spectroscopy. Molecular acid-base were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and equilibrium constant of pair formation were obtained. A crystalline transition of the EVA copolymer was observed and discussed in terms of enthalpy and entropy considerations based on FTIR and calorimetric DSC investigations. Fundamental results are then summarised to predict the interfacial reactivity of such polymer blends towards acid or basic substrates. 16 refs. 

A patent provides a means to eliminate solvent from the production process of a pressure sensitive adhesive. The typical method of producing pressure sensitive adhesive involves mastication of the elastomer, dissolving the elastomer and additives in a hydrocarbon solvent, coating the solution onto a backing, and drying to remove solvent. The phenolic tackifying resin of the invention eliminates the use of solvent process. 

Phenolic tackifiers (106) in the form of dispersions can be used to formulate neoprene or acrylic latex into waterborne contact adhesives. For example, a solid ratio of latex and phenolic dispersion (Union Carbide-BKUA-2370 or BKUA-2260)of 3 1 can form a stable adhesive at pH 6.0-6.5. 

Stearic acid is a usual processing aid in butyl rubber formulations, acting as lubricant and minimizing mill sticking apart from this action, it also plays the role of activator in the curing system. Hydrocarbon or phenolic tackifying resins are sometimes provided in compounds to assist the adhesion in confection or splicing. 

Hydrocarbon resins from petroleum are commonly used as a less expensive alternative to phenolic tackifying resins. These resins are commonly used in the tire industry however, they do not impart aged tack as good as phenolic tackifier resins. 

Hydrocarbon tackifiers are used as a less expensive but lower performing alternative to phenolic tackifiers. 

With the proper compounding adjustments, phenolic tackifiers can usually be used in place of hydrocarbon resins. However, phenolic tackifiers are generally more expensive. 

The f-butylphenol reacts with acetylene to produce acetylene phenol tackifying resin. Also, f-butylphenol reacts with formaldehyde to produce PF tackifying resins. 

Calcium carbide is a feedstock for producing acetylene-phenol tackifying resin. Calcium carbide is a feedstock to make 1,4-butanediol for curing polyurethane elastomers. 

A small amount of formaldehyde is reacted with alkylated phenols to make nonheat-reactive phenolic tackifiers, which are used to increase the building tack of rubber compounds. 

Isobutylene reacts with ammonia to make f-butylamine, an important feedstock in the synthesis of TBBS rubber accelerator, one of the two most widely used accelerators. Isobutylene is dimerized to make diisobutylene, which is used to produce octy-lated diphenylamine (a commonly used rubber antioxidant) and para-t-octyl phenol (a feedstock for the most common phenolic tackifier resin used by the rubber industry). 

Phenol reacts with olefins to produce f-butyl phenol, which reacts with acetylene to produce acetylene phenolic tackifying resins. 

Phenol reacts with diisobutylene to produce /hf-octyl phenol, which is used to produce phenolic tackifying resins. 

Heteroatom functionalized terpene resins are also utilized in hot melt adhesive and ink appHcations. Diels-Alder reaction of terpenic dienes or trienes with acrylates, methacrylates, or other a, P-unsaturated esters of polyhydric alcohols has been shown to yield resins with superior pressure sensitive adhesive properties relative to petroleum and unmodified polyterpene resins (107). Limonene—phenol resins, produced by the BF etherate-catalyzed condensation of 1.4—2.0 moles of limonene with 1.0 mole of phenol have been shown to impart improved tack, elongation, and tensile strength to ethylene—vinyl acetate and ethylene—methyl acrylate-based hot melt adhesive systems (108). Terpene polyol ethers have been shown to be particularly effective tackifiers in pressure sensitive adhesive appHcations (109). 

The second path in Fig. 3 outlines the approach to a more robust tape designed by Drew [21]. Here the milled rubber and filler are combined with tackifiers and other additives/stabilizers in an intensive dispersing step, such as a Mogul or Banbury mixer. Next, a phenolic resin or an alternative crosslinker is added and allowed to react with the rubber crosslinker to a point somewhat short of crosslinking. The compounded mixture is then charged to a heavy duty chum and dissolved in a suitable solvent like mineral spirits. To prepare a masking tape. 

The other class of acrylic compatible tackifiers includes those based on ter-penes. Terpenes are monomers obtained by wood extraction or directly from pine tree sap. To make the polyterpene tackifiers, the monomers have to be polymerized under cationic conditions, typically with Lewis acid catalysis. To adjust properties such as solubility parameter and softening point, other materials such as styrene, phenol, limonene (derived from citrus peels), and others may be copolymerized with the terpenes. 

Butyl phenolic resin is a typical tackifier for solvent-borne polychloroprene adhesives. For these adhesives, rosin esters and coumarone-indene resins can also be used. For nitrile rubber adhesives, hydrogenated rosins and coumarone-indene resins can be used. For particular applications of both polychloroprene and nitrile rubber adhesives, chlorinated rubber can be added. Styrene-butadiene rubber adhesives use rosins, coumarone-indene, pinene-based resins and other aromatic resins. 

In this section the rosins and rosin derivative resins, coumarone-indene and hydrocarbon resins, polyterpene resins and phenolic resins will be considered. The manufacture and structural characteristics of natural and synthetic resins will be first considered. In a second part of this section, the characterization and main properties of the resins will be described. Finally, the tackifier function of resins in rubbers will be considered. 

Tackifiers. Resins are generally added to adjust the desired tack. In general, resins must be used with plasticizers to obtain a good balance between tack and cohesive strength. Typical tackifiers are polyterpenes, although hydrocarbon resins and modified rosins and rosin esters can also be used. In some cases, terpene-phenolics or phenol-formaldehyde resins are added to increase adhesion. 

Tackifiers. SBRs have poor tack, so addition of tackifiers is necessary. The tackifier increases the wetting of the adhesive and also increases the glass transition temperature of the adhesive. Typical tackifiers for SBR adhesives are rosins, aromatic hydrocarbon resins, alpha-pinene, coumarone-indene and phenolic resins. 

Tackifiers. Phenolic resins are added to increase strength, oils resistance and resiliency of NBR adhesives. On the other hand, tack and adhesive properties can be improved by adding chlorinated alkyl carbonates. To impart tack, hydrogenated rosin resins and coumarone-indene resins can be added. 

Triacetin resistance is especially critical when filter tips are made in one location, stored, and then shipped to another location. For these operations, polyethylene-based adhesives are used because of their low polarity and therefore excellent resistance to triacetin. Where filter plugs are attached at the same location shortly after production, EVA-based adhesives are suitable and preferred. Both types of adhesives use low odor, clean tackifiers such as hydrogenated hydrocarbons or pure monomer resins (typically a-methylstyrene based). Rosin, rosin esters, and phenol-containing tackifiers are not acceptable. EVA-based adhesives use a higher level of wax (about 1 /3 of the formula) than polyethylene-based adhesives (5-20% wax) due to the lower crystallinity and slower set of EVA vs. PE. Application viscosities are 2000-5000 cP. 

Common plasticizers are used to reduce viscosity and to aid adhesion. Most plasticizers commonly utilized in PVC are also used in urethanes. One of the most common plasticizers is diisodecyl phthalate, though many others are used equally effectively. In some cases tackifiers, such as certain esters or terpine phenolics, are utilized to obtain specific adhesion characteristics. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Linear novolac resins prepared by reacting para-alkylphenols with paraformaldehyde are of interest for adhesive tackifiers. As expected for step-growth polymerization, the molecular weights and viscosities of such oligomers prepared in one exemplary study increased as the ratio of formaldehyde to para-nonylphenol was increased from 0.32 to 1.00.21 As is usually the case, however, these reactions were not carried out to full conversion, and the measured Mn of an oligomer prepared with an equimolar phenol-to-formaldehyde ratio was 1400 g/mol. Plots of apparent shear viscosity versus shear rate of these p-nonylphenol novolac resins showed non-Newtonian rheological behavior. 

Resorcinol is used primarily in the rubber industry for tyres and reinforced rubber products (conveyer belts, driving belts) and in high-quality wood adhesives, which are made from resorcinol, phenol and fonnaldehyde. It is also used in the preparation of dyes and pharmaceuticals, as a cross-linking agent for neoprene and a rubber tackifier, and in cosmetics (Lewis, 1993 Schmiedel Decker, 1993 Krumenacker et al., 1995). 

Tackifiers are used to increase the tackiness and the setting speed of adhesives. They increase tackiness by softening the poly(vinyl acetate) polymer in the wet and the dry adhesive film. Tackifiers are usually rosin or its derivatives or phenolic resins. Other additives frequently needed for specific application and service conditions are antifoams, biocides, wetting agents, and humectants. 

Resin as the Disperse Phase. Several kinds of resins (10) have been used to reinforce rubbers—e.g., phenolic or coumarone resins for natural rubber, styrene-butadiene resin for styrene-butadiene rubber, etc. One other important system, pressure-sensitive adhesive, also belongs to this class. These adhesives generally contain a low molecular weight resin functioning as a tackifier. In 1957, Wetzel (68) and Hock (19) found that these adhesives were actually two-phase systems (Figure 1). Under... 

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