Rosin ester tackifiers

Uni-Tac . [Union Camp] Rosin or rosin esters tackifiers for adhesives. 

In the second example (Table 2), two acrylic adhesive formulations are compared. The first contains a hydrogenated rosin ester tackifier, which shows relatively good UV stability. This tackifier can be replaced by one of lower stability (and lower cost), such as the nonhydrogenated rosin ester, by the incorporation of the appropriate light stabilizers. As these data show, some improvement in stability is seen when a BTZ is used at 0.5% (or a combination of BTZ/HALS at 0.25%/0.25%), but the best stability is achieved when the adhesive is stabilized with a HALS at the same level (0.5%). It should be pointed out that BTZs are commonly used in films and coatings (e.g., automotive clear coats) when the objective is to protect the material below the film. Similar applications can be imagined where UVA-containing adhesive films are used to screen and protect other substrates. 

Containing a mixture of 50% hydrogenated hydrocarbon and 50% pentaerythritol rosin ester tackifier. 

In static oven aging at 40°C (104°F) of a rosin ester tackifier (Fig. 10) the rate of hydroperoxide formation was reduced significantly using AO-2, with even better results using AO-3. The hydroperoxides are fairly stable at room temperature. At temperatures associated with hot-melt compounding or drying of solvent- and water-based formulations, hydroperoxides decompose spontaneously. The decomposition products initiate further reactions, which can result in the formation of color species. The addition of AO-2 and AO-3 which reduces the level of hydroperoxides formed, subsequently reduces the level of tackifier discoloration after oven aging (Fig. 11). 

Melt viscosity relates to stability during processing and to end-use performance. A stable melt viscosity is a very important property of a rosin ester tackifier. The melt... 

Figure 10 Stabilization of rosin ester tackifier. Hydroperoxide formation during oven aging at... 

Figure 11 Stabilization of rosin ester tackifier Gardner color after oven aging at 40°C (104°F).

The effects of storage time of an unstabilized and a stabilized rosin ester tackifier on the properties of an EVA HMA are illustrated in Figs. 15-17. Significant effects on the initial color of the EVA HMA (Fig. 15) are observed when using an unstabilized tackifier. An increased level of hydroperoxides is also noted. In this situation, the addition of an antioxidant to the HMA will not correct the problem. However, the addition of an antioxidant to the HMA may reduce further discoloration during compounding or end-use applications. 

Fig. 2. Chemistiy of rosin ester tackifiers. Rosin actually contains other components besides abietic acid.

The most common reason tackifiers are added is to improve the adhesion to non-polar plastics see Table 15.1. Rosin ester tackifiers added at 15-30% will normally increase the peel several fold on polyethylene and polypropylene surfaces. For more polar surfaces, terpene-phenolic or styrene-phenolics are added. Tackifiers are discussed in more detail in Sect. 15.5 below. Acrylics are compatible with only a narrow range of commercial tackifiers. Tackifier dispersions are available for water-based adhesives. 

Pentaerythritol in rosin ester form is used in hot-melt adhesive formulations, especially ethylene—vinyl acetate (EVA) copolymers, as a tackifier. Polyethers of pentaerythritol or trim ethyl ol eth an e are also used in EVA and polyurethane adhesives, which exhibit excellent bond strength and water resistance. The adhesives maybe available as EVA melts or dispersions (90,91) or as thixotropic, one-package, curable polyurethanes (92). Pentaerythritol spko ortho esters have been used in epoxy resin adhesives (93). The EVA adhesives are especially suitable for cellulose (paper, etc) bonding. 

Rosin ester resins are used extensively in pressure-sensitive adhesives as tackifiers. The adhesive is formulated by blending the resin with a polymer in solution or as aqueous emulsions. Typical compositions may contain about 50% resin. The glycerol or pentaerythritol esters of stabilized rosins are often used because they are stable on aging. 

In the earlier art, there was some consideration that partial incompatibility of the tackifier resin with the rubber was responsible for the appearance of tack, but this no longer is seriously held in light of continuing studies by many investigators. Aubrey [38] has addressed this in his review of the mechanism of tackification and the viscoelastic nature of pressure sensitive adhesives. Chu [39] uses the extent of modulus depression with added tackifier as a measure of compatibility. Thus in a plot of modulus vs. tackifier concentration, the resin that produces the deepest minimum is the most compatible. On this basis, Chu rates the following resins in order of compatibility for natural rubber rosin ester > C-5 resin > a-pinene resin > p-pinene resin > aromatic resin. 

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. 

Rosins and rosin derivatives. The resins more commonly used in rubber base adhesives are rosin esters, particularly glycerol and pentaerythritol esters, as well as rosins modified by disproportionation and hydrogenation. The glycerol ester of hydrogenated rosin has been reported to be an excellent tackifier for polychloroprene adhesives (see pp. 344-357 in [17]). 

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. 

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. 

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. 

Tackifiers. The tackifiers usually are hydrocarbon resins (aliphatic C5, aromatic C9) or natural resins (polyterpenes, rosin and rosin derivates, tall oil rosin ester). They improve hot tack, wetting characteristics and open time and enhance adhesion. The content on tackifiers in a hot melt can be in the region of 10-25%. 

A tackifier is hard low-molecular weight resin with a Tg higher than room temperature. It can give the highest tack to the adhesive when added at the proper amount. Petroleum resin, polyterpene, and rosin esters are typical tackifiers, which are all commercially available. 

Zonester . [Arizona] Rosin esters thermoplastic resin, tackifier for rubber, adhesives, contact cements, coatings. 

Depending on the properties required, the vinyl content in the EVA copolymer may be varied and varying quantities of tackifying resins (e.g., rosin esters) and waxes are incorporated. Tackifying resins affect the adhesion at elevated temperatures, the time the adhesive takes to harden and the quality of final adhesion achieved. The main purpose of the waxes is to reduce the melt viscosity and thereby improve the wetting of the substrates. 

As shown in rosin ester-based tackifiers, the addition of AO-2 can greatly reduce the hydroperoxide formation of aCs-hydrocarbon based tackifier during static oven aging at 40°C (104°F) (Fig. 13). 

Tackifying and adhesion-promoting resins (e.g., hydrocarbon, rosin esters, coumarone-indene, terpene resins)... 

CAS 65997-06-0 EINECS/ELINCS 266-041-3 Synonyms Rosin, hydrogenated Classification Thermoplastic acidic resin Definition Derived from hydrogenation of wood rosin Pre rerties Solid soften, pt. (R B) 68 C acid no. = 160 Uses Tackifier, modifier in adhesives and hot-melt-applied decorative, pressure-sensitive, and heat-sealable coatings prod, of rosin ester gum coatings on fresh citrus fruit component of food-contact articles fragrance in cosmetics... 

Dehnition Ester of pentaerythritol and hydrogenated acids from rosin Uses Tackifier for adhesives in protective and barrier-type coatings film-former in cosmetics defoamer in food-contact paper/paperboard in food-contact animal glue in wood preservatives for food contact Features Thermoplastic resin Regulatory FDA 21CFR 176.210, 178.3120, 178.3800, 178.3870... 

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