Hydrocarbon Resins for Adhesives: C5, C9, C5/C9, DCPD and Hydrogenated Types

Hydrocarbon resins, also called petroleum resins, are amorphous, low-molecular-weight hydrocarbon polymers that adhesive formulators add as tackifiers to hot melt and pressure-sensitive adhesives. In three example formulas of US patent 6,605,680 B1 they make up about 45 to 54 wt % of the finished adhesive (calculated from the stated parts).

Five commercial types exist: C5 aliphatic, C9 aromatic, C5/C9 aromatic-modified aliphatic, dicyclopentadiene (DCPD) and hydrogenated grades. Hydrocarbon resins are one of three tackifier families within the wider set of adhesive chemicals that formulators specify, beside rosin derivatives and terpene resins. Their generic CAS 64742-16-1 is a regulatory name. They have no CLP Annex VI entry (ECHA C&L: not classified, 95.07 %), are listed in 21 CFR 175.105(c)(5) and are not named in 21 CFR 175.125. In the EU, no specific measure covers adhesives as a whole (Regulation (EC) 1935/2004, Annex I group 2).

Sources and checks: identities and hazard classifications are read at ECHA and the issuing regulator, standards at the body that publishes them, and grade values at the data sheet named next to them; methodology and fact-checking explains each step.

Table 1 summarizes the generic petroleum resins entry.

What Is Hydrocarbon Resin?#

Hydrocarbon resin is a glassy, amorphous, low-molecular-weight polymer made by polymerizing unsaturated C5, C9 or dicyclopentadiene streams from steam cracking and sold to adhesive formulators as a tackifier. The C5 stream supplies 1,3-pentadiene (piperylene) and 2-methyl-2-butene; the C9 stream supplies vinyltoluenes, indene, styrene and alpha-methylstyrene; the third stream supplies cyclopentadiene and its dimer.

Hydrocarbon resins form one of the three classic tackifier families for pressure-sensitive adhesives (PSA). Aubrey (Rubber Chemistry and Technology, 1988) named rosin derivatives, terpene resins and petroleum resins; only petroleum resins come from cracker streams.

Identity: CAS 64742-16-1, EC 265-116-8 and a Generic EINECS Name#

CAS 64742-16-1 is the generic "Petroleum resins" identity, EC 265-116-8 in EINECS, and it names a UVCB substance with no single formula. The family hub on tackifier resins for adhesives sets this identity beside the rosin and terpene types. The EINECS definition of EC 265-116-8 describes a residuum-extract fraction, not a cationically polymerized resin, so this CAS on a data sheet is a regulatory identity and does not say whether a resin is C5, C9 or DCPD based. Each type carries its own CAS and ECHA list number (Table 2).

How Petroleum Resins Are Made from C5, C9 and DCPD Streams#

Three production routes exist: cationic polymerization, thermal polymerization and hydrogenation. The conditions each published patent states are listed below.

1. Cationic polymerization of the C5 cut uses an AlCl3/H2O/trimethylbenzene complex at 30 to 70 °C (86 to 158 °F) in 40 to 80 wt % solvent (US6605680B1).
2. Thermal polymerization of dicyclopentadiene runs at 240 to 320 °C (464 to 608 °F) for 4 to 20 h and gives a weight-average molecular weight under 1,000 g/mol (EP0665246A2).
3. Hydrogenation uses sulfided nickel-tungsten on gamma alumina at 200 to 320 °C (392 to 608 °F) and 20 to 300 atm (about 2.0 to 30.4 MPa) for 0.5 to 3 h (US4328090A).

Hydrogenation follows polymerization and saturates the double bonds that carry color: the Example 4 product of US4328090A reached Saybolt 27 to 30 at a softening point of 150 °C (302 °F).

What Does Hydrocarbon Resin Do in an Adhesive?#

A hydrocarbon resin dissolves in the matching polymer phase, lowers melt viscosity and raises the glass transition temperature (Tg) of the rubbery phase into the tack window. Optimum PSA tack lies about 20 °C (36 °F) above the adhesive Tg, according to producer guidance (Eastman, Adhesives & Sealants Industry, 2006), not a standard requirement. For a nonwoven adhesive in 37 °C (98.6 °F) service, the same article sets the adhesive Tg at 15 to 20 °C (59 to 68 °F).

Resin choice decides which phase receives the tack. Aliphatic resins keep the styrene domains of a styrenic block copolymer (SBC) intact, so the adhesive keeps a higher ring-and-ball softening point, while aromatic resins dissolve those domains. The viscoelastic basis of this behavior, including the Dahlquist criterion, is explained under tack in adhesives.

Types of Hydrocarbon Resin: C5, C9, C5/C9, DCPD and Hydrogenated#

Five types of hydrocarbon resin are sold for adhesive formulation: C5 aliphatic, C9 aromatic, C5/C9 aromatic-modified aliphatic, DCPD cycloaliphatic and hydrogenated grades of these. ExxonMobil's Escorez slate maps the same split: 1000 series aliphatic, 2000 series aromatic-modified aliphatic, 5300 and 5400 series hydrogenated cycloaliphatic, 5600 series hydrogenated aromatic-modified cycloaliphatic (Asia Pacific grade slate, 2018). Table 2 compares the five types and two related aromatic resins.

C5 vs C9 Hydrocarbon Resin: Aliphatic or Aromatic?#

C5 resin is aliphatic and tackifies the polyisoprene midblock of styrene-isoprene-styrene (SIS), natural rubber and polyolefins, while C9 resin is aromatic and associates with styrene endblocks and polar phases such as ethylene-vinyl acetate (EVA). Two producer cloud-point tests, not ASTM standards, measure the difference: a lower mixed methylcyclohexane aniline point (MMAP) means a more aromatic resin, and a lower diacetone alcohol cloud point (DACP) means a more polar resin.

In US patent 6,605,680 B1, raising the aromatic share from 96/4 to 65/35 lowers MMAP from 86 to 52 °C and DACP from 45 to 7 °C, and styrene-butadiene-styrene (SBS) loop tack rises from 0.4 to 24.2 N/25 mm. In that patent, the SBS adhesive tacks only with the aromatic-modified resin, while its SIS formula takes either resin. Table 3 sets the two patent resins side by side.

Hydrogenated, Water-White and Liquid Grades#

Hydrogenation saturates the double bonds of a hydrocarbon resin, giving water-white color and better heat and UV stability. The three grade facts below define the hydrogenated and liquid end of the range.

• Unhydrogenated thermal DCPD resin is about Gardner 16, so most DCPD adhesive grades are hydrogenated.
• Hydrogenated grades are measured on the Hazen scale: SUKOREZ SU-420 is a hydrogenated C5/C9 resin with a softening point of 120 °C (248 °F) and SU-230 a hydrogenated C5 resin at 130 °C (266 °F), typical values of Kolon Industries (pages read 2026-11-02).
• Liquid C5 resin makes up 27 wt % of a published SIS label hot melt PSA, beside 41.6 wt % solid C5 resin (Adhesives & Sealants Industry, article 93852).

Grades and Key Properties: Softening Point, Tg, Molecular Weight and Color#

Across ExxonMobil's Escorez grade slate, typical ring-and-ball softening points run from 86.2 to 139.5 °C (187.2 to 283.1 °F), so a resin specification names the grade and its measured values rather than a class value. Table 4 lists each property with the grade family, producer and document behind it.

The C9 row tops the Escorez slate, so a family name such as C5 or C9 does not fix a softening point; the purchase specification states the measured value of the grade and the method behind it.

Data sheets report color on three different scales, Gardner, Yellowness Index (YI) and Hazen, so a specification names the scale with each color number.

Compatibility and Loading in Hot Melt and Pressure-Sensitive Adhesives#

In US patent 6,605,680 B1, hydrocarbon resin makes up about 50 wt % of an SIS hot melt PSA (120 of 242 parts, calculated), and Table 5 gives each chemistry's share with its basis.

Hydrocarbon Resins in EVA and Polyolefin Hot Melts#

In EVA packaging hot melts, the resin is chosen by its compatibility with the EVA. In US6605680B1, EVA blend cloud points across the tackifiers tested fall between 60 and 74 °C (140 and 165.2 °F).

Metallocene polyolefin hot melts carry a lower resin share. EP3541887B1 claims 10 to 40 wt % hydrocarbon tackifier with 10 to 50 wt % metallocene ethylene interpolymer, wax and 0.1 to 2 wt % antioxidant, and its method claim applies the hot melt at 121 °C (249.8 °F) or less.

Hydrocarbon Resins in SIS and SBS Hot Melt PSAs#

In the US6605680B1 SIS hot melt PSA, hydrocarbon resin is the largest component, and it tackifies the polyisoprene midblock. The three formulas below add the detail Table 5 leaves out.

• US6605680B1 SIS formula: the resin is the patent's C5 or C5/C9 resin, the oil is a naphthenic process oil and the antioxidant is antioxidant 1010.
• US6605680B1 SBS formula: the second polymer is a styrene-butadiene random copolymer, with the same naphthenic oil and antioxidant 1010.
• In two examples of Adhesives & Sealants Industry article 87867: a tape formula of SIS 43 / C5/C9 resin 52 / oil 4 / antioxidant 1 wt %, and an elastic-attachment formula of SIS 30 / hydrogenated DCPD resin 50 plus endblock resin 5 / oil 15 wt %.

The midblock tackifier sets the elastomer-phase Tg: Kraton gives a target of -10 to 10 °C (14 to 50 °F) for the tackified elastomer phase of a label PSA (Adhesives & Sealants Industry, 2007).

Hydrocarbon Resins in Acrylic PSAs#

The examples of US patent 6,280,557 B1 use 11 to 25 parts tackifier per 100 parts acrylic polymer, hydrocarbon resins among them. With the hydrocarbon resin Regalrez 6108 at 20 parts, the peel on high-density polyethylene is 4.4 N/25 mm (1.0 lbf/in), and 17.2 N/25 mm (3.9 lbf/in) with 7.5 parts plasticizer (both at 30 cm/min). That patent prefers hydrogenated rosin esters.

Processing, Handling and Storage Notes#

Hydrocarbon resins ship as flakes, pastilles or pellets, and liquid grades also exist. Melt color stability is a specified property: the Escorez 5415 sales specification of 9 February 2021 sets 61.0 YI maximum after 5 h at 175 °C (347 °F).

Producers stabilize synthetic tackifier resins with antioxidant 1010: 0.1 to 0.5 % in synthetic tackifier resins (typical product value, BASF Irganox 1010 data sheet, October 2022), never a limit. A purchase specification states the three handling items below.

• Supply form: flakes, pastilles, pellets or liquid.
• Thermal color limit, with its test time and temperature.
• Antioxidant type and level in the resin as delivered.

Hazard Classification and Regulatory Status#

Petroleum resins (CAS 64742-16-1, EC 265-116-8) have no CLP Annex VI entry, and their ECHA C&L notified classification is not classified. Table 6 gives the status of the generic identity with the date each status was read.

The type identities follow the same pattern; every minority notification above 5 % is listed. C5 resin (26813-14-9), C5/C9 resin (62258-49-5, notification inactive) and DCPD resin (68132-00-3) are not classified (100 %). C9 resin (71302-83-5) is not classified (64.05 %), also notified by a minority as Skin Sens. 1 H317 (20.26 %) and as Skin Sens. 1A H317 with Aquatic Chronic 3 H412 (15.69 %). Coumarone-indene resin (63393-89-5) is not classified (60.71 %), also notified by a minority as Eye Irrit. 2 H319 (39.29 %). Hydrogenated 69430-35-9 is not classified (88.89 %), also notified by a minority as Eye Irrit. 2 H319 (11.11 %); the other four hydrogenated identities are not classified (100 %). None has an Annex VI entry, and none except EC 265-116-8 shows an active REACH registration.

What a Hydrocarbon Resin MSDS Shows#

A hydrocarbon resin safety data sheet (SDS, formerly MSDS) states the identity and hazards of its own grade, not of the resin class. Where section 3 gives the generic CAS 64742-16-1, it names the regulatory identity only. The product SDS beats the generic class line, so a formulator reads sections 2 and 3 of the SDS for the grade bought.

Are Hydrocarbon Resins Allowed in Food-Contact Adhesives?#

In the United States, 21 CFR 175.105(c)(5) lists petroleum hydrocarbon resins by manufacturing description for food-packaging adhesives, while 21 CFR 175.125 for pressure-sensitive labels and tapes names none of them. The (c)(5) entries cover hydrogenated cyclopentadiene-type resin, hydrogenated styrene/vinyltoluene/indene resin, resins from dienes and olefins of aliphatic, alicyclic and monobenzenoid arylalkene types, CAS 68239-99-6 and 68441-37-2, alpha-methylstyrene-vinyltoluene 1:3 resins, coumarone-indene and phenol-coumarone-indene resins. Section 175.105 covers dry food, and fatty or aqueous food only as trace amounts at seams and edge exposure or behind a functional barrier; the finished adhesive label reads "food-packaging adhesive", beside the CLP rules covered under hazard labeling and SDS for adhesives.

Section 175.125 names terpene resins and rosins (through 21 CFR 178.3870) instead (eCFR, 1 October 2026), so a label or tape PSA cannot rely on that list for a hydrocarbon resin.

In the European Union, Regulation (EC) 1935/2004 lists adhesives as group 2 of Annex I, the materials that may be covered by specific measures, and no specific EU measure covers adhesives as a whole. Good manufacturing practice under Regulation (EC) 2023/2006 applies, because its Article 2 covers every Annex I group.

Regulation (EU) 10/2011 on plastics reaches adhesives through Article 2(1)(b), which covers plastic multilayers held together by adhesives. Migration testing of finished food-contact adhesives is covered on the regulation page.

Alternatives to Hydrocarbon Resins: Rosin Esters and Terpene Resins#

Rosin esters, polyterpene resins and terpene-phenolic resins replace hydrocarbon resins where polarity or a 21 CFR 175.125 listing matters. Table 7 compares the three.

Kraton's tackifier brochure 26-03 ranks the three on a qualitative solubility-parameter chart: polyterpenes lowest, rosin esters between, high-hydroxyl terpene-phenolics highest, with similar values likely to be miscible.

The hazard identities differ as well. Rosin (CAS 8050-09-7) carries CLP Annex VI 650-015-00-7 Skin Sens. 1 H317. Plain glycerol and pentaerythritol rosin esters have no Annex VI entry, and neither do hydrocarbon resins.

Hydrocarbon Resin HS Code, Price Factors and Sourcing#

Hydrocarbon resins enter the United States under HTS 3911.10.00.00 ("Petroleum resins, coumarone, indene or coumarone-indene resins; polyterpenes") at a 6.1 % general duty. For an adhesive raw material buyer, the heading does not separate a C5 grade from a C9 or terpene grade. Producers and distributors by family are listed under adhesive raw material suppliers.

No price is given here; a quote depends on the five factors below.

1. Resin type: C5, C9, C5/C9, DCPD or hydrogenated.
2. Hydrogenation level: none, partial or full.
3. Softening point range, with its method.
4. Color, on the named scale.
5. Quantity, supply form and delivery country.

Regalrez, the hydrocarbon resin of the acrylic PSA example, belongs to Synthomer, owner of the former Eastman adhesive resins business since 1 April 2022.

Each request is passed straight to independent companies of that trade, and no company pays AdhesiveAdditives.com to be named or to receive requests; the editorial policy explains how.

How Are Hydrocarbon Resins Tested and Specified?#

A hydrocarbon resin specification names five measured values: ring-and-ball softening point, glass transition temperature, molecular weight, color and cloud point (MMAP or DACP). Softening point follows ASTM E28-18(2022), an active standard whose reference method uses automated apparatus, and Tg follows ASTM D6604-00(2022), the differential scanning calorimetry method for hydrocarbon resins. Apparatus, editions and the other cloud-point and softening-point methods are compared under softening point testing of resins.

Is Hydrocarbon Resin the Same as Rosin?#

No: hydrocarbon resin is a synthetic polymer made from petroleum cracker streams, while rosin is a natural UVCB mixture of abietic-type resin acids obtained as gum, wood or tall-oil rosin. Rosin (CAS 8050-09-7) carries CLP Annex VI 650-015-00-7 Skin Sens. 1 H317. Hydrocarbon resins have no Annex VI entry; both appear in 21 CFR 175.105, while only rosins appear in 175.125.