CA1255040A - Liquid polysulphide/polyepoxide copolymers - Google Patents

Abstract

ABSTRACT

Stable liquid adduct compositions are prepared by an addition reaction between epoxy-terminated polymers and mercaptan-terminated polymers. One of the polymers is in stoichiometric excess so that the composition has free epoxy or mercaptan functional groups. The liquid polymer composition can be stored for long periods before curing with a curing agent reactive with the free functional groups.

Description

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BA~KGROUND OF rrHE INVENTION
Field of the InventiQn The present invention relates to liquid copolymers of mercaptan-terminated polymers such as polysulphides and epoxy-terminated polymers such as epoxy resi~s which can be stored as prepolymers before final curing to form 6 olid products.
Descri~tion of the Prior Art The production o~ resins by coreacting poly6ul-phides with polyepoxides in the presence of a catalyst is well known. The reaction between the mercaptan groups of the polysulphide and the oxirane groups of the polyepoxide prooeeds easily and i6 the basis of`US-A-

2 789 958, which describes the production of resinous reaction products of polyepoxides and polysulphides and methods of making them. All but one of the examples given in the US-A-2 789 958 describe the reaction between liquid polysulphides and so-called polyepoxide curing agents in the presence of amine catalysts. The cured products were hard, tough, sometimes rubbery materials.
In the other example, the polysulphide polymer was reacted with the polyepoxide awring agents, in the absence of amine catalyst, at 70 C for BiX hours and at 25'C ~or two days. The product was a tough rubbery polymer.
The invention de~cribed in the US-A-2 789 958 formed the basi6 for the use of liquid polysulphide polymers as flexibilizer~ for polyepoxy resins. In these systems the liquid polysulphide polymer is mechaniaally mixed into the polyepoxide resin together with a catalyst, usually a tertiary amine. ~he resulting products are tough, impaot resistant ~olids, which if nedessary adhere to a wide range of substrates.
~he products o~ Guch proces~es have been used in the .

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production of adhesives, coatings, electronic encapsulation systems~and mouldings.
GB-A-787 022 describes self-hardening resins made by mixing liquid or semisolid epoxide resins and liquid aliphatic saturated polythiopolymercaptans. These resins generally cure to a hard rubbery state within 24 hours or in a few cases 48 hours.
Despite their undoubted success as tough, chemic-ally resistant coatings and adhesives, current LPJepoxysystems suffer from the limitations of a mercaptan odour emanating from the polysulphide component, which persists until the system begins to cure.
US-A-3 101 326 discloses the reaction of a poly-sulphide with styrene oxide to reduce or eliminate themercaptan odour. The product can be used to flexibilise epoxy resins.
SUMMARY OF THE INVENTIQN
According to the present invention there is provided a curable li~uid polymer composition having a stable viscosity prior to curing, said composit~on containing a copolymer formed by an addition reaction between epoxy - groups of an epoxy-terminated polymer having at least two epoxy groups per molecule and mercaptan groups of a mercaptan-tsrminated polymer having at least two mercaptan groups per molecule, one of said polymers being in stoichiometric excess whereby the copolymer has free epoxy or mercaptan groups.
In composition~ having free epoxy groups, the odour of mercaptan i6 eliminated.
The .invention also provides a process for producing a composition as defined above which comprises reacting an epoxy-terminated polymer having at least two epoxy groups per molecule with a mercaptan-terminated polymer having at least two mercaptan yroups per molecule, one of ~' l~, . , . .. . . . , .. , . _ ,, said polymer6 being in stoichiometric excess whereby the final product has free epoxy or mercaptan groups.
The composition thus produced can be stored for subsequent curing with a curing agent reacting with said epoxy or mercaptan groups to give a solid copolymer.
~he basis of this invention ie that stable liquid prepolymers can be formed by a direct, uncatalysed, reaction between liquid polymers with terminal or pendant mercaptan groups and solid or liquid polymers with terminal oxirane groups. The oxirane groups are in stoichiometric excess over the mercaptan groups or vice versa. This ensures that the amount of chain extension is limited thus Xeeping the viscosity increase resulting from the coupling of the two polymers to a minimum.
The products of the invention reprssent a new class of liquid polymer composition containing block copolymers, with alternating blocks of polysulphide and polyepoxide and with éither oxirane or mercaptan end groups depending on the relative proportions of the two components in the initial reaction mixture. These liquid copolymers can be stored until required for final curing, when the residual reactive groups in the copolymer can participate in further chain extension reaction, using conventional epoxide or polysulphide curing agents, to produce a range of solid polymers with useful commeraial applications.
~he products of the invention preferably have a viscosity not higher than 100 pas, more preferably less than 60 pa6, at 25 C. Their molecular weight is usually in the range o~ 1600 to S000, preferably not more than 3000.
The reaction of the invention is preferably aarried out at temperatures from 10 to 120'C, and it can conveniently be carried out at relatively low temperature~ such a6 10-50-C, and typ.ically at 20~C. Increased reaction rates and lower viscos.ity can be obtained using relatively higher temperature~ such as 60 C. The reaction can be carried out by 5 simple admixture of the two components in the desired proportions, the mixture then being allowed to stand until the reaction is complete. The reaction mixture may include a solvent.
The composition of the invention will normally include as a major component block copolymers of the epoxy- and mercaptan-l0 terminated polymers.
The ideal ~tructure for the block copolymer would be an ABAstructure for the block polysulphide molecule capped with two polyepoxide molecules:

o OH OH o ~ -POLYEPOXY-(!~HCH2-S-POLYSULPHIDE-SCH2-CH-POLYEPOXY ~

or a polyepoxide molecule capped with two sulphide molecules OH o~
HS-POLYSULPHIDE-S-CH2-CH-POLYEPOXY-~H-CH2-S-POLYSULPHIDE-SH

Typical adducts of thi~ type would have molecular weights of about 1700. A typical polymer composition of the invention will also contain the exces~ polymer in unreacted form.
Le~s desirable ~tructùres for the copolymer would be:

~ -POLYEPOXY-POLYSULPHIDE-POLYEPOXY-POLYSULPHIDE-POLYEPOXY-',~

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and HS-POLYSULPHIDE-POLYEPOXY-POLYSULPHIDE-POLYEPOXY-POLYSULPHIDE-SH

and higher analogues, with molecular weights of 3000 or more.
The viscosity of the latter analogues would be greater than these achieved with he ideal structure~. The copolymers of the invention do not necessarily have exclusively the ideal structures, but preferred formulations, in accordance with the invention, favour a predominance of the ideal structures in the final product. ~rhe invention is not limited to the use of difunctional pol y6 ul phide polymers and difunctional polyepoxide polymers, that i5 polymers with two functional groups per polymer molecule. Polymers with a~functionality greater than two can also be used to produce the liquid products. However polymexs with functionality much greater than two would produce solid products or liquid products with unmanageably high viscosity.
Tha copolymers produced by the chemistry described in this invention are :referred to as adducts. rrhere are basically two types:
(i) Tho e formed from a stoich$ometria excess of oxirane groups over mercaptan groups. 'rhe resulting liquid polymar products have no residual mercaptan groups, have no mercaptan odour and have free oxirane groups, which can be opened in chain extension/cross linXing r~actions using the catalysts commonly used i~ epoxy resin technology. The products in (i) are known as the excess epoxy adducts.

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Those formed ro~ a sto~ch~ometxic exce$s of ~ercaptan groups over ox~rane g~oups. The result~ng l~gu~d polymer products have no res~dual oxirane groups, might retain a mercap-tan odour and have free mercaptan groups, whtch can be reacted using curing agents commonly used in polysulphide polymer technol-ogy, for example manganese dioxide. The - products in (ii) are known as excess mercaptan adducts.
The composition containing excess epoxy adducts can be used in all the technologies where currently epoxy resins or polysulphide plus epoxy resins are used. The formulation may be simple, where cure of the adduct alone is effected ~y the addition of a catalyst such as a tertiary amine, or it might ~e more complex, with the addition to the adduct of particulate fillers, chopped fibre~, plasticizers, pigments etc. precading the cure with the catalyst. The excess epoxy adduct may also be blended with other liquid pol~mers, such as polyepoxide polymers, polysulphide polymers, polybutadiene polymers, poly~utadiene~coacrylonitrile pol~mers. Where the polymers have suita~le reacti~e groups such as carboxylic acid, amine, mercaptan or hydroxyl, co-re~ction with the oxirane groups is feasible. With or without co~reaction the adduct would be expected to enhance a property or properties of the second polymer, for example, tear ~trength, adhesion or chemical resistance. The technologies in which the liquid adduct can be used include adhesives, coatings, primers, electronic encapsulation, sealing compounds, mouldings and the manu~acture of composites.

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The excess mercaptan adduct can be uGed in technologies where mercaptan polysulphide polymers are currently used. Cure and cross linking can be effected through the use of agents capable of oxidising mercapta~
groups into disulphide linkages, ~uch as inorganic peroxides, dichromates and permanganates or organic hydroperoxides. It i8 customary, although not essential, to form compounds of liquid poly~ulphide polymers with particulate fillers, plasticizers, thixotropic agents, adhesion promoters etc. Similar compounding principles would apply to the excess mercaptan adduct. The excess mercaptan adduct may also be blended with other liquid polymers such as polysulphide polymers and polyepoxide polymers where the mercaptan groups in the adduct would co-react with the mercaptan group and oxirane groups respectively of the other polymers. The excess mercaptan group adduct could also be blended with high molecular weight solid polysulphide polymers, which also contain free mercaptan groups for co-reaction. The addition of the adduot to any one o~ these polymers would be expected to enhance one or more properties in the cured product, ~uch as tear etrength, adhesion, elastic recovery and abrasion'resistance.
To understand the theory o:E adduct manufacture certain terms associated with epoxy resins and liquid polysulphide polymers must be explained.
Epoxy Group Conten~
~his term is used herein to mean the number of molecules of epoxide groups in 1 kilogramme of epoxy-terminated polymer.
Units = moles/Rg.

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L~ 3Y~L_ Çonten~
The -SH mercaptan content of liquid mercaptan-terminated polymers is usually quoted as a percentage. F'or the co-reaction with Epoxy-terminated polymers it is more useful to express the mercaptan contsnt in the same units as the Epoxy Group Content i.e. moles/Kg.
e.g. LP-33 (described in more detail below) has a mercaptan content of 5.76%
i.e. in l Kg of LP-331there is 0.0576 Kg of mercaptan groups.
The number of moles of mercaptan per Kg =
weight of mercaptan qroup in l K~ of Polysulphide Molecular weight of mercaptan group.
The molecular weight of the Mercaptan group = 0.033 Kg.
Therefore the number of moles of -SH in l Kg of LP-33 =
o.05?~ = l.75 moles/Kg.
0.033 i.e. Mercaptan content of LP-33 = l.75 moles/Kg.
In the case of the excess epoxy adduct, a 1 : l weight ratio has been found to give satisfactory results, and a polyepoxi~e/poly~ulphide weight ratio of 2 : 1 has been ~ound to be particularly advantageous ~rom the point of view of low viscosity. Generally, the proportions are preferably selected 60 that the molar ratio of epoxy groups to mercaptan groups is in a range from 2 : 1 to 7.5 : 1, more preferably 2 : l to 5 : l.
In ths case of the excess polysulphide adduct, lower molar excesses of mercaptan groups are generally pre~erred, typically in the range l.5 : l to 3 : 1. In terms of polysulphide/polyepoxide weight ratios, the prs~erred range is from 3 : l to 6 : l.
The mercaptan-terminated polymers usually have an average molecular weight of 500 to 1200, preferably not more than 2000. The viscosity is pre~erably 0.5 to 2.5 Pas and the mercaptan content i6 preferably 1.5 to 2.5 mole/kg.
Mercaptan-terminated polysulphide polymers which are particularly suitable for the purposes of the invention are characterised by the fact that they have recurring polysulphide linkage between organic radicals having at least two primary carbon atoms which are connected to disulphide linkages. Typical examples of disulphide 0 polymers are those corresponding to the general formula:
H~-(-RSS-)X-RSH
in which each R is an organic polyvalent radical, preferably predominantly divalent alkylene o~ahydrocarbon or thiahydrocarbon radicals, examples of which ara given in US Patent 2,789,958, and X is a number greater than one and may vary from a relatively small number in the case of liquid polymers having a molecular weight of about 500 to 12000, e.g. 3 to 100 where R is -(C-CH2-CH2-)-, to a relatively large number in the case of solid polymers which may have a molecular weight of about 100,000 to several million. The low molecular weight polysulphide polymers e.g. 500 to 12000, are normally liquids at 2S C and are preferably formed by the reaction of an organic dihalide with a backbone corresponding to R
with an inorganic polysulphide e.g., Na2Sy,y usually being greater than two. Solid organic poly6ulphide polymers are produced thereby which may be split according to the method of US Patent No. 2,466,963 to provide liquid polythiol polymers.
Preferred liquid polysulphides used in the preparation of the li~uid product6 of the invention are those manufa~tured by Morton Thiokol Incorporated and known as LP'~. Three grades in particular will be exemplified:

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In the manufacture of Excess Epoxy Adducts, the use of LP-33 produces adducts with lower and more stable Vi 8 C OS ities than those based on LP-3.
Thi6 is probably due to the lower percentage of trifunctional component present in the LP-33 (of 0.5% in LP-33 and 2% in LP-3). Trifunctionality provides æven more site6 for chain extension and polymer cross linking by the mercaptan-epoxy co-reaction. Cros~ linking and chain extension leads to higher adduct molecular weights and therefore higher vi6cosities.
Further research'has shown that the use of a liquid polysulphide with no trifunctionality would produce adducts with vi~cosities that are lower and more stable than those ba6ed on LP-3 and LP-33. ZL 1400C i~ one suitable "zero cross-link" form of LP.
A8 polyepoxy polymers for thP preparation of the li~uid polymer products of the invention, various commercially available epoxy resins can be used. The 20 polyepoxide polymers used are usually liquid, although the chemiaal principles pertain to solid polyepoxide polymers also.
The preferred polymers have an average molacular weight of 250 to 600. The preferred epoxy group content 25 is in the range from 2 to 6 mole/kg. When a liquid polymer i~ used it6 viscosity is preferably 0.5 to 20 Pa~. ~iquid epoxy resins formed from epichlorohydrin and bisphanol A and sold under the trade marks "EpiXote" and "Araldite" are particularly suitable. The properties of 30 some o~ these epoxides are as follows:-~., .

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Heavy duty, industrial epoxy coatings are based on solid epoxy resins. These system6 are supplied with the epoxy resin dissolved,in solvent. Solid epoxy coatings are said to provide superior corrosion and environmental resistance to the liquid Epikote 828 type coatings albeit with some 108s of aured coating flexibility. The present invention envisages the use of such solid epoxy resins in forming stable liquid adducts.
One suitable type of solid epoxy resin which may be used in Shell Epikote 1001, which has an epoxide content of 2:1 mole/kg.
It is al~o possible to use low molecular weight polyfunctional glycidyl compounds. ~hese are often referred to as reactive diluents by manufacturers of polyepoxide polymers. An example is Anchor Chemiaals Heloxy 68, which has an epoxy molar mass of 135-155g, a viscosity at 25 C of 1-16 m Pas and an average epoxide content of 6.89 mole/kg. (Heloxy is a Registered Trade Mark).
The following examples are given to explain more fully the nature of the pre~ent invention, but are merely illustrative and are not to be construad as limiting the 6cope of the invention as defined by the claims.

Exampl ç_1 200 grammes of LP-33 were intimately mixed with 200 grammes of Epikote 815. The mixture was allowed to stand at 25 C and after one week it was noted that the meraaptan ~roup concentation, as measured by standard analytical procedure, had fallen to ~ero, and the odour of hP-33 had di~appea~ed. The ratio of Eplkote 815 5¢~

to LP-33 taken at the start represents a molar ratio of

3.0 to 1 of oxirane groups to mercaptan groups. The viscosity of the product adduct after two weeks was 34.9 Pas (at 25 C). After six months storage at rvom temperature the viscosity was measured again and shown to be 34.5 Pas (at 25 C). This low viscosity was found still to be maintained after 36 weeks.
100 grammes of the product adduct were cured with S
grammes of the amine, tri-dimethylaminomethylphenol. The cure characteristics and the physical properties of the cured product were compared with those obtained using, freshly mixed, 50 grammes of Epi~ote 815, 50 grammes of LP-33 and 5 grammes of the same amine curing agent.

... .... ....... ... .. . . ... .. ..

The results, shown in Table 3, indicate that the cured adduat exhibits the toughness obtained with the LP-33JEpikote 815 control mix.

Table 3 Epikote 815 and LP-33 Adduct C~ntrol MiX

Gel ~ime (mins.) 60 30 Cure exotherm ( C) 40 60 Abrasion re6istancea 8.57 7.21 Tensile 6trength (MPa) 9.77 10.60 Elongation to Break (%) 15 25 Impact Strength (lb in)b 160+ 160+
Flexibility OK OK
Hardnes 8 ( Shore D) 59 63 a. DuPont Abrader. Yolume loss per 1000 revolutions.
b. Falling weight. 160 lb in is the maximum figure obtainable.

Ex~mp~e 2 200 gramme~ of Epikote 817 were intimately mixed with 200 grammes of ~P-3. The mixture was kept at 40 C
and after 1 week the mercaptan level had fallen to zero and the odour of LP-3 had disappeared. The ratio of Epikote 817 to LP-3 taken at the start represents a molar ratio o~ 2.07 tp 1 of oxirane groups to meroaptan groups. Th~ same reaction mix was also kept at room ~;~5S~

temperature, when the mercaptan content fell to zero after three week6. The vi5c08ity of the adduct formed at room temperature wa6 initially 91.1 Pas, after 8 week~
83.9 Pas and after 6 months 82.1 Pas. There was little change from this figure after 36 weeks. It had no LP-3 odour. Viscosity was measured at 25 C. 100 grammes of the product adduct were cured with 5 grammes of the amine, tri-dimethylaminomethylphenol. The oure characteristics were compared with those obtained using, freshly mixed, S0 grammes of Epikote 817, 50 grammes of LP-33 and 5 gramme~ o~ the same amine curing agent. ~he results are B hown in Table 4.

Table 4 E~ikote 817 and LP-3 Adduct ~ CQntrol ~ix Gel Time tmins) 40 30 Cure exotherm ( C) 25 50 Abra~ion resistanoe 8.7 4.7 Tensile ~trength (MPa) 8.32 10.05 Elongation to break (%) 55 95 Impact strength (lb in) 160l 160+
Flexibility ' OR OK
Hardnes 5 ( Shore D) 56 45 ~.255i~

Example 3 200 grammes of Epikote 213 were intimately mixed with 200 grammes of LP-3. The mixture was stood at room temperature and aftzr two weeks the mercaptan content had fallen to zero and the smell of LP 3 had disappeared.
The ratio of Epikote 213 to LP-3 taken at the start represents a molar ratio of 2.32 to 1 of oxirane groups to mercaptan groups. The viscosity of the adduct when first formed was 45.6 Pas (25'C). After 4 months it was 41.3 Pas (25 C).
The adduct of Epikote 213 and LP-3 was cured with different levels of tri-dimethylaminomethylphenol. The results are shown in Table 5.

Table_~

Wëight of Curative (grammes) 5 10 20 Weight of adduct (grammes) 100 100 100 Work life (hours) 1.5 1.0 0.5 Cure exotherm ( C) 27 30 34 Time to solid (hours) 6 3 Hardness (3 days. Shore D) 35 45 65 Example 4 200 ~rammes of Epikote 816 were intimately mixed with 200 grammes of LP 33. The mixture was kept at room temperature and after 16 days the mercaptan content had fallen to zero and the odour of LP-33 had disappeared.
The ratio of Epikote 816 to LP-33 taken at the start rapresents a molar ratio of 2.8 to 1 of oxirane groups to mercaptan groups. The ViBCoSity of the adduct when ~irst formed W~15 31.~ Pas (25C) Afler 3 rr,2nlh was 33. 0 Pas (25C~.
Ex a mple 5 2û0 ~rar: mes of Araldite 495S were intimately rr.ixed with 2~û grammes Or LP-33. The mixture was stood at ~0CC.
hfter one week the mercap-an content had fallen to zero and the odour Or LP-33 had disappesred. The ratio o~
Araldite 4955 to LP-3 taken at the start represent a m~lar of 3.2 to 1 ot oxir~ne groups to mercaptan groups. The viscosi~y Or the adduct when first lor7red was 46.9 Pas (25C). After six weeks it was 47~ Pas . 125C).
E x a mple 6 250 grammes of Epikote 828 were mixed with 1000 srammes of LP-3. The mixture was kept at room temperalure and ~fter 24 weeks the oxirane . concentration had fallen to zero~ The r~tio of LP-3 to Epi)cote 828 t~ken at ~he slart represents a molar ratio of lu62 to 1 of mercaptan groups to oxirane groups. The viscosi$y of the product was 66 . 0 Pas ~25'C3.
lOt) grammes of the product were mixed with 34. 5 gramm~s of a paste con5i5tin~B f 10 ~rammes o~ act~ve ~nan~anese dioxide, 12.5 grammes of ~i liquid chlorinated paraffin and D.S ~rammes o~ ;e2ra methylthiuram disulphide.
- The mix cured tD sn elastc)meric in 90 minutes .
Exam~e 7 The foliowin~ Excess Epoxy Adducts were manufactured by mixing the liquid polysulphide component with the epoxy resin at 1: 1 by weight ratio:
Epikote 213 + LP-3 Epikote 213 ~ LP-33 6~

Epikote 8l6 ~ LP-3 Epiko~e 816 ~ LP-33 0.4 X~ batches of each system were manufactured an~
S stored at both room temperature and 40C. The mercaptan content viscosity and epoxide content o~ each batch ~einB
monitored on a weekly basis over a 6 month stora~e period.
The following room temperaîure stored Excess Epoxy Adducts were found to have stable, low viscosities at the end of the 6 month stora~e period:
Epikote 213 ~ LP-3 ~c.40 Pas ~.
Epikote 213 ~ LP-33 (c.30 Pas ) Epikote 816 + LP-3 (c .50 Pas ) Epikote 816 + LP-33 (c .3~ Pas ) (:)f the 40C stored Adducts, the followinE~ exhibitecl viscosity stability for 17 to 20 weeks:
Epikote 816 ~ LP-3 ~c.70 Pas ) Epikote 816 ~ LP-33 [c.40 Pas ) The Epikote 213 ~ LP-3 and LP-33 40C stored Adducts exhibited viscosity stability for lCI to 12 weeks, remaining well below 50 Pas . in each sase.
Examl)le 8 The modification_ of Epikote 828 with epoxy dil-~ents_ to Droduce stable low viscosity Excess Epox~dducts The ~ollowing diluents were used:
1. . Anchor Chemicals Heloxy MK ~16 A mono-~unctional hi~h molecular weight aliphatic glycidyl ether diluent was mixed with the Epikote 828 in the following proportions P~rts by wt.
E:pikote 828 100 Heloxy MK 116 20 -2~ Anch~r Chemic~ls Heloxy ~C 68 A difunctional reactive glycidyl ether. i~c~oxy 68 - i5 21 technical ~r~de of neopentyl ~lycol di6]ycidyl ether which has low volatility.
The diluent ~as mixed with the Epikote 82B in the following proportions:
Parts lby wt.
Epikote 828 l oo Heloxy WC 68 39 Jo Viscosity Or modiried EE~oxy resin = 1 Pas l`he diluent ~nodified Epikote 828 systems were mixed with ~he liquid polysulphide componen- at a 1 1 by weight ratio to form the following Excess Epoxy Adducts :-Epikote 828 ~ Heloxy 116 ~ LP-3 Epikote 828 ~ l~eloxy 116 ~ LP-33 Epikote 828 ~ Heloxy WC 68 ~ LP-33 These adducîs were stored at room temperature and 40~C. The following r~sults were obtained.
1. The Heloxy 116 sample5 were store~ Sor up to 17 weeks and exhibiled viscosities in the 35 to ~5 .
Pas region for the Er~ikote ~8 ~ LP-3 variety and 25 to 3~ Pas for the Epikose 828 ~ LP-33 variety, 2. The Epikote 828 t Heloxy WC 68 ~ LP-33 ~dduct sa.nples were both stable after 10 weeks storage, with adduct viscosity very low at l5., to 25 Pas~
3. Th~ Heloxy 116 samples required 4 weeks storage to form ~dducts while the Heloxy ~YC 68 samples ~ormed ~dducts in 2 to 3 weeksO

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. Neither Heloxy rnodified Epikote B28 ~ Lt' adducts h~ve had at the time of ~ilin,~, su~ficient stora e time for a full assessment to be made of their viscosity stability .
S Example 9 ~ e use of a "Zero cross-link" LP to Droduce stable _. _ _.A ~
lo~ viscosity Excess_~oxy Adducts The zero percentage cross link LP used in this examp~e was ZL-1400C. The analytical data obtained from Morton Thiokol Inc. in the V.S.A. on ZL-1400C is outlined below:
Sample ~SH Viscosity at 25~C
- ZL-1400C ti.21 1. 82 Pf~6 - - The following Excess Epoxy Adducts were manufactured 15- - by mixing the ZL-I400C with the epoxy resin component at a 1: 1 by weight mix ratio:
Epikote ~28 ~ 0% Cross~link LP (ZL-1400C) MY 750 ~ 0% Cross-link LP ~ZL-1400t::~
XD 4955 ~ 0% Cross-link LP (ZL-14()0C) MY 778 ~ 0% Cross-link LP ~L-1400C) An "in house" diluent modified Epikote 828 was also mixed ~t a 1: 1 ratio with the ZL-1400C to prod~ce the Excess Epoxy Adduct :-Epikote 828 ~ Heloxy WC 68 ~ 0,6 Cross-link LP (ZL-1400C~
Samples were stored at room temper~ture and at 40GC for up to 6 monlhs.
Table 6 illustrates clearly the effect of mercaptan polyfunctionaliSy on adduct viscosity and oYeral]
viscosity stability for the room temperature stored samples:

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1 The results of the evaluation of the use of zero cross link polysulphide in adduct formation leads to the following conclusion 1. The use of a zero-crosslink liquid polysulphide produces Excess Epoxy Adducts with lower and more stable viscosities than those manufactured from LP-3 and LP-33.
2. Adduct viscosity and viscosity stability is governed by the polysulphide component in the following manner:

..~DECREASING % TRIFUNCTIONAL COMPONENT

^ 15 LP-3 LP-33 ZL-1400C

DECREASING ADDUCT VISCOSITY
IMPROVED VISCOSITY STALILITY

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1 Example 10 A 1:0.5 weight mix ratio adduct of Epikote 828 and LP-33 was manufactured in 150 kg and 50 kg batch sizes to determine whether the properties associated with the small-scale adduct manufacture of Examples 1 to 9 are similarly applicable to larger production size quantities.
The bulk adduct mixes were manufactured by simple admixing of the LP and epoxy components in steel drums. The bulk mixes were manufactured and stored at room temperature.
0.4 and 5 kg samples of the same adduct were produced for comparison purposes.
- The bulk adduct manufacture was found to be accompani^e* by a reaction-exotherm-which ra-ised the temperature of the mix from 21C to 39C ie an increase of 18C. This exotherm was present in both the 50 kg and 150 Xg batches but was not detected in the 0.4 kg or 5 kg samples.
The rates of adduct formation for the four batch sizes are set out in Table 7 which shows that the larger the adduct batch size, the more rapid the rate of adduct formation.

25Batch Size Time to Adduct formation at Room Temp.
(kg) (Days) 300.4 21 -~ 28 It was also found that the bulk adducts exhibit a lower storage viscosity and a superior viscosity stability when compared to the smaller 0.4kg batch sample.
Table 8 illu~t~ates these points.

~ 2~5~

STORAGE PERIOD SAMPLE VISCOSITY
at 20 - 25 C AT 20 - 25C (Pas) WEEKS
150 Kg Sample 50 Kg Sample0.4 Kg sample 0 5.8 6.8 4.0 1 54.4 62.2 35.0 3 46.0 47.3 44.0 6 49.1 5~.6 36.0 40.8 ~2.0 45.0 12 50.6 46.2 S0~6 1~ 38.8 34.0 53.0 17 35~ 36.0 53.0 32.6 35.0 23 46.1 45.7 26 43.0 46.5 39 38.0 36.0 5~

1 E~ample 11 A 1:0~25 by weight mix ratio of Epikote 1001 and LP-~3 was prepared.
The epoxide content of this adduct can be calcul-ated as follows:
Epikote 1001 Epoxide content = 2.1 moles Kg LP-33 Mercaptan content = 1.75 moles Kg Therefore a 1:0.25 weight mix ratio of Epikote 1001 and LP-33 has in 1.25 Kilos of sample:

2.1 moles Kg. - 1.75 moles Kg = 1.66 moles of excess

4 - Epoxide.

In 1 Kilo of sa~ple there is ] 25 moles = 1.33 moles of excess Epoxide.
Thus, the epoxide content of a 1:0.25 Epi}cote 1001 ~ LP-33 Adduct = 1.33 moles Kg The solid Epikote 1001 was ground into a fine powder using a mortar and pestle.
S0 grammes of this powdered resin was weighed into a three necked round-bottomed flask and 12.5 grammes of LP-33 added. Approximately 10 grammes of Methyl-e~hyl ketone was added as a solvent and the mixture stirred well using a mechanical stirrer.
Heat was gradually applied via a heating mantle.
When the temperature of the mix reached 60C the system became semi-solid. At 70C the mix was fluid and easily stirred.
The heatinq source was removed when the temperature of the mix reached 70C. The temperature of the mix continued to rise peaking at 80C (this may be due to a reaction exotherm) and then cooled gradually to room temperature. Virtually all the solvent was removed during the heating process and as a result the room temperature mix was very viscous but definitely ~,5~

1 not solid. After three days standing at room temperature in the sealed round bottomed flask the mixture had lost its mercaptan odour. Infra-red analysis confirmed that there were no mercaptan groups present in the mix indicating that an adduct had been formed.
The adduct was subsequently used in the following high solids surface coating formulation Pbw 10 1:0.25 by weight Epikote 1001 + LP-33 adduct 30 K-54 Curative 3 Methyl-ethyl-ketone 5 The coating was doctor-blade applied onto alumin-ium and shot blasted mild steel plates The formulation had the following cure characteristics:
Pot life (38g cup size) = 1~ hours Tack free time as a thin film on steel - 2 - 4 hours.

', ! ~ _ ~5q~

_xampl e 12 A 1:0.25 by weight mix ratio adduct of Épikote 1001 and ZL-1400C was formulated into a white coloured 79h solids content solvent-based coating and spray applied onto stee1 Q-Panels and shot blasted mild steel substrates. The cured coatings resistance to cold salt spray, UV exposure and heat ageing was eYaluated.
Formulation *Partsby Weight 1:0.25 Epikote 1001 ~ ZL-1400C 100 Titanium dioxide 2~
*
~'8eetle 640"flow promoter 20 "Ancamine 1608 curative 4 MethylEthy7 Keton~ : Xylene ~100:50) 40 Results . .
~Coating Appearance = Very high gloss finish.
Average Coating Thickness - 150 1. Cross-Hatch Adhesion B5-3900 Part E6 Cross-Cut Test Initial After 240 hrs. After 480 hrs. After 240 hrs. A~ter 120 hrs.
Salt Spray Salt Spray UY Exposure Heat Ageing Exposure Exposure at 70C at 70C
. _ O O O O
Excellent Excellent Excellent Excellent Excellent 2. Marr Resistance A5TM D 3363 Film Hardness by Pencil Test ~ . . . _ , - . lnitial After 240 hrs. After 480 hrs. After 240 hrs. After 120 hrs. Salt Spray Salt Spray UV Exposure Heat Ageing Exposure Exposure at 70C at 70C

* Trade mark * * Trade mark .

~'~55¢~

3. Reverse ~mpact Resistance (Falling Weight Method) lnitial After 240hrs. After 480 hrs. After 240 hrs. A~ter 120 hrs.
Salt Spray Salt Spray UV at 70C 70C Heat Ageing , . _ . _ . . _ . _ . _ . _ >18 Joules 13.6 Joules 2.3 Jou1es 4.5 Joules <2.3 Joules . Elonqation of Coating with Conioal Mandrel Apparatus ., .
Test Method ASTM D-522 Coating elongation ~ 30%
S. Corrosion Resistance BS-3900 Part F4 There was no evidence of corrosion spread, paint film delamination or blistering after 240 hours continuous cold salt spray exposùre.

~2~

Exampl e 13 An epoxy coating oomposition was prepared using an Epikote 828/LP-33 adduct as an addikive, The formulation was as follows:
, Parts by Weiqht Epikote 1001 100 (1:0.5 Epikote 828 ~ LP-33) Resin 25 Titanium dioxide 155 Beetle 640 20 Ancamine 1608 11 Methyl ethyl ketone : Xylene ~100:50) 83 Cured Coati n~ Test Results Coating appearance: High Gloss Finish Average Coating Thickness: 500 - 800 ~m .. . . , .. ,.~ , .

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--3~-- _ Example 14 A 1:0.25 by weight mix ratio adduct Of Eplkote 1001 and LP-33 was evaluated as a primer system for a two part polysulphide sealant on a concrete substrate. Ihe adduct based primer was applied as a 50~,0 solids content solution onto concrete (formulation outlined below) and the primer~sealant sysLem tested according to BS 4254 for adhesion and cohesion in tension.
The primer was allowed to become tack free before the polysulphide sealant was applied.
Technical Details . _ .
- 1. Primer Formulation Parts by Weight ; 1:0.25 Epikote 1001 + LP-33 Adduct 100 EDA Adduct 870 Curative* 24 Methyl-ethyl ketone 124 Drying time of primer system on concr~e = 30 minùtes * EDA Adduct 870 curing agent is a chemical adduct of a solid epoxy resin with ethylene diamine. The curative is manufactured by Anchor Chemical tUK) Limited.
2. Polysulphide Sealant Systern The polysulphide sealant used in this evaluation was a two component manganese dîoxide cured 35% polymer content sealant. The mix ratio by weight of Base : Curing Paste was 275:22.5.

........... .

~255~

The results of the BS-4254 tests are set out in Table 9.

s Samples Specification Limits Results Initial 25N - 270N 100 nm2 MaxirnuT failure at149N 147 N
150% E:xtension NF

~'ater 25N - 270N 1002 131 N 129N
Imnersion Maxirnwn failure atNF
150% Extension 15 Heat Aged 25N - 270N -100 mn'134N 132N
Max~Nm failure at NF
100% Extension Note NF indicates no adhesive or cohesive failure.
20 INITIAL refers to the tensile stress at 150% strain on test specimens where the sealant has been allowed to cure for 7 days at 25 - 2C and 50 - 5~ r.h. prior to testing.
WATER IMMERSION r~fers to the tensile stress at 150%
-25 strain on test specimens which have been totally imrnersed in water for 7 days at 25 - 20C subsequent to the INITIAL conditioning period HEAT AGED refers to the tensile stress at 100% strain on test specimens which have been heat aged in a 30 ventilated hot-air oven at 70 _ 2 C for 7 days subseq uent to the INITIAL conditioning period.

These results show that the adduct based prim~r has allowed the polysulphide sealant to meet the requirements of BS-4254 with regard to tensile adhesion to concrete.

....

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--3~--X fi mpl~ 1 5 ~e effect Or altering the Epoxy/LP mix ratio on Adduct Vi scosity Epikote 828 ~ Zero c~oss-link LP Excess E?oxy Adducts were manu~actured from the followin~g EPOXY
LP weight mix ratios :-EPOXY : Zero Cross-link LP
~ . 5 :
1 . 3 1 . 5 The adducts were stored at room tempera~ure and their viscosities monitored on a weekly basis.
The 1 : 0.5 systern formed an adduct after two : 15 weeks storage at room temperature. After three weeks storage the initial adduct viscosity had remained ~t ~irca 35 Pas~
The 1: I mix formed an adduct after three weeks with viscosity pealcing ~t . 80 Pas at the time o~ adduct formation. Adduct viscosity then stabilised at circa 60 Pas for the remainde:r o~ the storage period of 21 weeks.
The 1 : 1.3 mix system formed an addllct after three weeks storage. Adduct viscosity peaked ~t 123 Pas at the point of formation but then stabilised at 8~
Pas. This stability had been maintained after seven weeks storage.
The 1 : 1.5 mi~ system tormPd an adduct after four weeks s~orage with a viscosity of 1~4 Pas at the time of adduct formation. The resulting adduct showed no viscosity stability,. After 14 weeks the adduct had virtually gelled.

~ .

, -3~-These experiments lead to the following conclusions:
1. Decreasing the Zero cross-link LP component leads to a lower viscosity Excess Epoxy Adduct which exhibits improved storage stability.
2. The lower the Zero cross-link LP component the more rapid is the formation of an Excess Epoxy adduct.
3. Zero cro6s-link LP : Epoxy weight ratios greater than 1 : 1 produce unstable, high viscosity, Excess Epoxy Adducts.
The followin$ 1 : 0.5 Epoxy : LP mix ratio adducts were also manufactured and stored both at room temperature and 40 C. Their viscosities being monitored on a weekly basis:
1 : 0.5 Epikote 828 + LP-33 (25-40 Pas) 1 : O.S MY 778 + LP-33 ( 20 Pas) 1 : 0.5 MY 778 + 0% Cross- ( 15 Pas) link LP
It is significant to compare their initial behaviour with thosa of their 1 : 1 mix ratio counterparts.
1 : 1 Epikote 828 + LP-33 (70-80 Pas) 1 : 1 MY 778 + ~P-33 (30-40 Pas) 1 : 1 MY 778 I 0% Cross- ( 60 Pas) link LP
Clearly the viscosities of the 1: 0.5 Excess Epoxy Adducts are lower, at both room temperature and 40 C, than the 1 : 1 Excess Epoxy Adducts at the corresponding storage times.
For both LP-33 and the zero Cross-link LP altering the Epoxy : LP mix ratio from 1 : 1 to i : 0.5 has the effect of:
a) reducing the vi6cosity of the resulting Excess Epoxy Adduct.

) Producin~ Excess Epoxy Adducts ~ ith ~upcrior viscosity s~ability.
Ex~mple 1 6 The cure o~ ~elected_low viscosity Excess Epoxy Adducts ~he following low viscosity Adducts were cured with 5 parts by weight of tridimethylaminomethylphenol curative to 100 parls of Adduct.
Epikote 816 ~ LP-3 Epiko~e 816 ~ LP-33 Epikote 213 ~ LP-3 Epikote 213 ~ LP-33 Epikote 828 ~ Heloxy 116 ~ LP-3 Epikote 828 ~ Heloxy WC 68 ~ I.P-33 - Table 10 eompares the ~gel time and cure exotherm f these adducts with - their-~canventional l,PfEpoxy~-coun2e~r-parts. The LP~Epoxy eontrols were eured with 10 parts by ~weight of tridimethylaminomethylphenol to 100 parts Or epoxy component,.
The results indicate that Adducts exhibit a longer gel time and lower eure exotherm than the LP,~Epoxy controls .
TABLE 10 - ADDIX~ CURE
- Adduct (a ) Cont rol (b) Gel Time Cure ( C ) Gel Time Cure ( C 1 2~ (mins iExothe~m (mins ) Exothelm Epikote 816 ~ LP-3 105 33 40 80 Epikote 816 ~ LP-33 160 23 S0 64 Epikote 213 ~ LP-3 140 32 30 83 Epikote 213 ~ LP-33 105 29 50 70 Epikote 828~1elc~ 68 ~ LP 096 XL 140 29 30(i) 70~i Epi kot e ~;28~el a~y ~:68 I LP~33 301ii ) 60tii ) Epikote 828~elo~r 116 ~ LP-3 90 27 30ti) 70(i) Epikote 828~elax!y 116 ~ LP~33 120 27 30(ii) 60~ii) . , ~2~

(i ) Epikote 815 ~ LP-3, mixed in-situ ~ -(ii) Epikote 815 ~ LP~33, mixed in-situ.

(a) Adduct cured with 5 pbw or tridimethylaminomethyl-phenol to 100 parts Or Adduct.
(b) Controls cured with 10 pbw of tridimethylaminomethyl-phenol to 100 parts of Epoxy component.

The Physical Properties o~ Cured Excess Epoxy Adducts The Excess Epoxy Adducts cured with 5 parts by weight of tridimethylaminomethylphenol were subsequently com-pared with their LP~Epoxy Controls for:
a) Cured Hardness b) Abrasion Resistance - 15 c~ Tensile Strength/Elongation at break d) Flexibility e) lmpact/Adhesion The comparative results are shown in Tables 11 to 15 Conclusions a) Cured Hardness Adduct hardness values are very similar to those Or the Controls b~ Abrasion Resistance The abrasion resistance values Or the cured adducts 2~ are ~enerally superior to those of the Controls.
c) Tensi ~ on~atio at break Adduct tensile strength and elongation at break values are lower than those exhibited by their LP~
Epoxy control cvunterparts. This may be due in parl to the presence of voids in the Adduct test pieces. LP-33 ba5ed Adducts however tend to have tensile strength values which approach those Or the LP-33 based controls.

':, ' .1 ~2~
,cj_ d ) Flexibility In gener~l both Adducts and controls have comparable flexibility. Only the Epikote 816 ~ LP-33 Adduct is more brittle than its LP/Epoxy counterpart e) Im?act/Adhesion Wi~h the exception of the Epikote 816 ~ LP-33 Adduct the impact/adhesion results for the controls ~nd Adducts are very comparable.

HARDNESS RESULTS

AdductControl Hardnes~Hardness Shore DShore D

Epikote 816 + LP-3 55 54 Epikote 816 + LP-33 45 50 Epikote 213 + LP-3 47 50 Epikote 213 + LP-33 50 55 (i )(ii ) Epikote 828 + Heloxy WC68 + LP-3 0% X-L 58 45 56 Epikote 828 + Heloxy WC68 + LP-33 59 63 Epikote 828 ~ Heloxy 116 + LP-3 S5 45 56 Epikote 828 + Heloxy 116 + LP-33 60 59 63 ~i) Epikote 815 + LP Adduct from Example 1.
20(ii) Epikote 815 + LP Control, mixed in situ.

~ 25~4~

ABR~SU~LT~
~PONT ABR~SI ON TESTER

UNITS = VOLUME LOSS PER 1000 REVOLUTIONS

Addu~t 5~Q~E~

Epikote 816 + LP-3 3.45 3. 52 Epikote 816 ~ LP-33 3. 92 4. 2 Epikote 213 + LP-3 2. 87 2.81 Epikote 213 + LP-33 2. 36 2. 41 (i) (ii) Epikote 828 + Hel oxy WC68 ~ LP-3 0% X-L 3.11 5. 76 6. 75 Epikote 8 28 + Hel oxy WC68 + LP-33 8. 57 7. 21 Epikote 828 + Heloxy 116 + LP-3 4. 84 5. 75 6. 75 Epikote 828 + Heloxy 116 + LP-33 4. 88 8. 57 7. 21 ~0 ~ pikote 815 + LP Adduot from Example 1.
(ii~ Epikote 815 + LP Control from example 1.

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EXAM LE 1l The following curatives were evaluated with both the Exce6s Epoxy Adducts and their LP/Epoxy controls:
Anchor 1608 Ancamine 17 6 8 Ancamide 502 Ancamine MCA
Triethylene tetramine The chemical nature and level of each curative u6ed to cura the Adduct~ and control~ are described in Table 16 below:
~ , Table 16 Curative Chem1c~1 Viscosity at Parts by W~. Qf ~urati Description 25 C to 100 Part6 Q~:
(a) (b) Adduct Epoxy in the Control Anchor 1608 Liquid aliphatic 36 12.5 25 amine adduct Ancamine 1768 Activated Liquid 3 10 20 aliphatic amine Ancamide 502 Liquid Aliphatic 3.5 25 50 amido amine Ancamine MCA Liquid Cyclo- 2.5 27.5 55 aliphatic amine Triethylene- Liquid aliphatic 5 10 tetramine amine ~he objectives of curative study were:
1. To observe the mi6cibility of the curative with the re~in during mixing.
2. To measure the gel time, tack free time and exotherm of each curative/resin system.
3. To measure the cured hardness of these 6y~tems.

5q~

4. To measurs the volume swell of the cured products after immersion in water at room temperature and 60 C.
To date the following Adduct and corresponding control resins have been studied:
Epikote 816 + LP-3 Epikote 816 + LP-33 Epikote 213 + LP-3 Epikote 213 + LP 33 The results of th~ Curative study are given in Table 17 to 28 and ~ummarised below. Depsnding on the property required, recommendations are made on the selection of curing agents fr~m the ones studied.
1 : 1 EPIKOTE 816 +_LP-3 EXCESS EPOXY ADDUCT
1 : 1 EPIKOTE 816 + LP-3 PARAMETERS RECOMMENDED CURA.TIVE
Optimum Adduct/Curative Ml~cibility Anchor 1608 Ancamine MCA
Rapid Cure Anchor 1608 ~ Triethylene tetramine Optimum Water Resistance Ancamine 1768, Ancamide 5Q2 and Triethylene tetramine at 60 'C immersion and Triethylsne tetramine at 22'C immersion ~ 1 EPIKOTE 816 + LP-33 EXCESS EPOXY ADD~CT
PARAMETER -~ECOMMENDED CURATIVE
~ptimum Adduct/Curative mi~cibility Anchor 1608 Rapid Cure Anchor 1608 Optimum Water Resistance Triethylene Tetramine or Ancamine 1768 at 60'C
immersion Triethylene tetramine or , Ancamine 1768 or Anoamine 50 at 22'C.

. ~.. . . ,. , .. _ , . . _ ....

-48~
1 : 1 EPIROTE 213 + LP~3 EXCESS EPpXY ADDU~T
PARAMETER RECOMMENDED~yRATIVE
Optimum Adduct/Curative miscibility Anchor 1608 Ancamine MCA
Rapid Cure Anchor 1608 Optimum Water Resistance Ancamide 502 or Triethylene tetramine at 60 C immersion Ancamine 1768 at 22 C
immersion 1 : 1 EPIKOTE 213 ~ LP-33 EXCESS EPOXY ADDUCT
PARAM_?ER EcOMMENDED~cy-RATIvE
Optimum Adduct/Curative miscibility Anchor 1608 Ancamide 502 Rapid Cure Anchor 1608 Optimum Water Resistance Tristhylene tetramine at 60 C immersion.
Ancamine 1768 at 22 C
immersion.

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EXAM~PLE_18 The physical properties of a cured 1:0.25 Epikote 1001 + LP-33 adduct were tested. The adduct was evaluated as an unfilled, spatula applied coating on shot bla~ted mild steel plates. The coating was cured with Ancaminæ 1608, an aliphatic amine. The cure characteristics of the coati~g are tabulated as follows:

~,..
EPOXIDE ANCAMINE THIN FILM

OF ADDUCT1 LEVEL phr FREE TIME
Moles Rg HOURS
...... .
1:0.25 Epikote 1001 + ~P-33 1.03 4.12 8 ", , . . ... ~

Two samples of adduct, differing only in coating thicknes 6 were prepared. The 6 amples were aEses 6 ed or adhesion, impact, salt pray and W resistance. The test results are shown a~ follows:
~am~le A S~mp~ B
Coating thickness (~) 300-350 110-260 Cross--hatch adhesion * 0 0 Reverse impact (inch lb~) >160 >160 Dire¢t Impact (inch lbs) >160 80 Cros6 Hatch Adhesion 0 Reverse Impact (inch lbs) 160 ~F~E~ 200 HQUR~_ALT S~RAY EXPOSUR~
CroEs-Hatch Adhesion 0 Corro6ion Protection No Corrosion Spread No Lo~6 of adhesion No loss of ~lexibility -~;

-61a-* Cross hatch adhesion is assessed on a scale graded from zero to six. A reading of zero implie~ excellent adhesion. A reading of 5iX = poor adhesion.

., . . , .. , ....... , .. . , .. , ., .. ~, . .. .

~ 2~

ADDUCl MICR~S~RUCTUR~

Cured 6ample6 of the I : 1 Exccss poxy Adduc~
Epiko~e 213 ~ LP-33 and the I : ~ Epik~te 213 ~ LP-33 C~ntrol were ~ubjected to Transmission El~ctron Mi~cro-~copy examination ~f their microstructure.
S ~hree ~amples were ~nalysed:
a) ~ : I Epikote 2~3 ~ LP-33 Control cured at room temperature ~i~h 10 pbw of EH-330.
b) 1 : 1 Excess Epoxy Adduct Epikote 213 ~ LP-33 cured ~t roDm temperature with ~0 pbw of EH-330.
~0 c) I ~ I ~xce&s Epoxy Adduct Epikote 213 ~ LP-33 cured for I hour ~t 60~C wi~h 10 pbw of EH-330.
lt was antieipated tha~ the Shree ~amples would ~how a different ~icrostructure because of their different ~odes of ~anufacture and temperature of cure;
The te~t result~ arc as ~oll~ws:.
1. All the samples have a microstructure indicative of two phasc materials.
2. ~he disper~ed phase believed to be the LP-33 ~ st finely dispersed in the roo~ temp~rature cured Exce~s ~poxy Adduck ~ample. Degre~ of dispersion being ranked .in the order:
Room Temp. Cured Adduct~ LP/Epoxy Control ~>
60C Cured Adduct.

g, ~:g ~,d j

Claims (31)

The embodiments of the invention in which an exclusive property or privilege is claimed axe defined as follows:

1. A process for preparing a curable-liquid block copolymer which comprises reacting an epoxy resin having an epoxy group content of 2 to 6 mole/kg, with a mercaptan-terminated polymer having at least two mercaptan groups per molecule and a molecular weight not exceeding 2000, one of the reactants being in stoichiometric excess but the epoxy/mercaptan group molar ratio being not in a range from 2:1 to 7.5:1 or in a range from 1:1.5 to 1:3, to give a block copolymer having free epoxy groups or free mercaptan groups respectively characterized in that the reac-tion is carried out in the absence of a catalyst or curing agent at a temperature in the range from 10 to 50°C in the case of liquid epoxy resin and at an elevated temperature sufficient to produce a fluid reaction mixture put not exceeding 120°C in the case of a solid epoxy resin, to give a curable liquid block copolymer composition which has a stable viscosity prior to curing.

2. A process according to claim 1 which comprises the steps of:
grinding a solid epoxy resin into a fine powder, adding to said powder a liquid mercaptan-terminated polymer in an amount such that the epoxy groups of the epoxy resin are in stoichiometric excess over the mercaptan groups of the liquid mercaptan-terminated polymer;
adding a solvent to the resulting mixture and heating and stirring the mixture in the absence of a catalyst or curing agent at a temperature not exceeding 120°C to dissolve said epoxy resin and react it with said liquid mercaptan-terminated polymer and produce a curable liquid block copolymer having free epoxy groups.

3. A process according to claim 1, wherein said epoxy resin is a liquid resin having a viscosity from 0.5 to 20 Pas.

4. A process according to any one of claims 1 to 3, wherein said epoxy resin has an average molecular weight of 250 to 600.

5. A process according to any of claims 1 to 3, wherein said mercaptan-terminated polymer is a liquid polysulphide.

6. A process according to any of claims 1 to 3, wherein said mercaptan-terminated polymer has a viscosity from 0.5 to 2.5 Pas.

7. A process according to any of claims 1 to 3, wherein said mercaptan-terminated polymer has an average molecular weight of 500 to 2,000.

8. A process according to any of claims 1 to 3, wherein the molar ratio of epoxide groups in the epoxy-resin to mercaptan groups in the mercaptan-terminated polymer is in the range from 2:1 to 7.5:1.

9. A process according to claim 1, wherein the reaction product is stored as an uncured liquid polymer composition and subsequently cured with a curing agent to form a solid product.

10. A process according to claim 9, wherein the reaction product contains free epoxy groups and said curing agent is an amine.

11. A curable liquid polymer composition having a stable viscosity when stored for at least two weeks at 25°C prior to curing, said composition containing a polymer formed by an addition reaction between epoxy groups of an epoxy polymer having at least two epoxy groups per molecule and an epoxy content of not more than 6 mole/Kg and mercaptan groups of a polysulfide polymer having at least two mercaptan groups per molecule, said polysulfide polymer being in stoichiometric excess whereby said curable liquid polymer has functional mercaptan groups.

12. The liquid polymer composition of claim 11 which is made by an uncatalyzed reaction.

13. The liquid polymer composition of claim 11 which has a viscosity of not more than about 100 Pas at 25°C

14. The liquid polymer composition of claim 13 which has a viscosity of not more than about 60 Pas at 25°C.

15. The liquid polymer composition of claim 11 which has a molecular weight in the range from about 1600 to about 5000.

16. The liquid polymer composition of claim 15 which has a molecular weight of not more than about 3000.

17. The liquid block copolymer of claim 11, wherein the major component of the copolymer is in the form of an ABA block copolymer.

18. The liquid polymer composition of claim 11, wherein the molar ratio of mercaptan groups to epoxy groups in the original polymers is in the range from about 1.5:1 to about 3:1.

19. A process for preparing a curable liquid polymer composition having a stable viscosity when stored for at least two weeks at 25°C prior to curing, which comprises reacting an epoxy polymer having at least two epoxy groups per molecule and an epoxy content of not more than 6 mole/Kg with a polysulfide polymer having at least two mercaptan groups per molecule, one of said polymers being in stoichiometric excess, in the absence of a catalyst, at a temperature of from 10°C to 60°C, whereby said curable liquid polymer composition has terminal functional groups selected from one of epoxy groups and mercaptan groups.

20. The process of claim 19, wherein said epoxy polymer has an epoxide content of from about 2 to 6 mole/kg.

21. The process of claim 19, wherein said epoxy polymer is a solid.

22. The process of claim 19, wherein said epoxy polymer is a liquid resin having a viscosity from about 0.5 to about 20 Pas.

23. The process of claim 19, wherein said epoxy polymer has an average molecular weight of from about 250 to about 600.

24, The process of claim 19, where said poly-sulfide polymer has a viscosity from about 0.5 to about 2.5 Pas.

25. The process of claim 19, wherein said poly-sulfide polymer has an average molecular weight of from about 500 to about 12,000.

26. The process of claim 25, wherein said poly-sulfide polymer has an average molecular weight of from about 500 to about 2000.

27. The process of claim 19, wherein said polysulfide polymer has an average of from 2 to about 2.5 mercaptan groups per molecule.

28. The process of claim 19, wherein said polysulfide polymer has a mercaptan content of from about 1.5 to about 2.5 mole/kg.

29. The process of claim 19, wherein the reaction product is stored as an uncured liquid polymer composition and subsequently cured with a curing agent to form a solid product.

30. The process of claim 29, wherein the reaction product contains epoxy groups and said curing agent is an amine catalyst.

31. A process for preparing a curable liquid polymer composition having a stable viscosity when stored for at least two weeks at 25°C prior to curing, which comprises reacting an epoxy polymer which is a solid having at least two epoxy groups per molecule and an epoxy content of not more than 6 mole/kg with a polysulfide polymer having at least two mercaptan groups per molecule, one of said polymers being in stoichiometric excess, by heating a mixture of said polymers, in the absence of a catalyst, to about 70°C, then removing the source of heat and allowing the reaction to proceed to completion.