Chuong 3 Alkyd+Polyester VN N

7/22/2019 Chuong 3 Alkyd+Polyester VN N

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Chng 3: NHA ALKYD & POLYESTER

3.1 Nha Alkyd.

Nha Alkyd (Alkyd resins) i din cho mt h Polyme c dng trongcht to mng nh gi thnh r v d s dng. Thut ng alkyd c

gi do Kienle and Ferguson bt ngun t al ca alcohol v cid ca acid;

cid sau c i thnh kyd, tuy nhin, nha polyeste khng no trong

backbone khng c gi tt l alkyds m dng : "unsaturated polyesters."

nh ngha ca alkyds m t c chp nhn rng hn l alkyds l

nha polyester bin tnh vi acid bo (fatty). Cc nha resins khng bin

tnh c gi l polyester bo ha (saturated polyesters). Cc thut ng

nh akyd khng du oil-free alkydv polyester bin tnh vi du oil-modified polyester cng c th c tm thy trong cc ti liu.


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3.1.1 NGUYN LIU TNG HP NHA ALKYD:

- Polyol - Polyacid - Du hoc acid bo


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Phn loi

Alkyds c tng hp t ba thnh phn c bn: polybasic axit, polyols,v (ngoi tr alkyds khng du) fatty acid. Tnh cht v t l ca ccthnh phn quyt nh nhng tnh cht ca resin. S lng kt hp l rtln, v c im k thut ca mt alkyd resin lin quan n nhiu sthng s.

nh hng hm lng du v Loi duTy thuc vo t l phn trm trng lng ca acid bo trong resin,alkyds c gi tt l du ngn gy(short oil) ( 55%). Tuynhin, mt s tr ngi c lin quan n cc thut ng.

i khi du di cp n t l phn trm Triglyceride, trong ctrng hp t l acid bo phi c tnh li sang Triglyceride. Mtcch gn ng: trng hp 1 = trng hp 2/1,045.

Cc loi acid bo c dng cng nh hng ng k n tnh cht cacc alkyds. Alkyd resins c phn loi kh, bn kh (semidrying), vkhng kh (nondrying), ty thuc vo mc bt bo ha (unsaturation)trong cc acid bo (tr s iodine > 140, 125 n 140, v


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Qu trnh kh oxi ha (Oxidative) nha alkyds, gm vic oxidation tkhng kh n cc ni i trong cu trc thnh phn acid bo, ti akhong 50% i vi du bo (di). Sau khi kh, cng mng phim t lnghch vi mc bin tnh acid bo.

Alkyds du gy thng cho phim cht lng cao i vi mu sc v duytr bng tt, nhng cho mm do thp v bm dnh (adhesion)km. Alkyds du bo thng rt tt cho qu trnh phn tn bt mu(pigment dispersion), tnh cht l bin, lu tr n nh.

V d v cc tnh cht ca alkyd resins lin quan n hm lng du vcc loi du c hin th trong bng sau:

Oil Type Oil

Length

(%)

Typical Oil Properties

Oxidizing >60 Linseed, safflower, soybean,

tall oil fatty acids; wood oil in

blends with other oils;

dehydrated castor oil

Soluble in aliphatic solvents;

compatible with oils and medium oil

length alkyds; good drying

characteristics; films are flexible, with

reasonable gloss and durability

Oxidizing 4555 Linseed, safflower, soybean,tall oil fatty acids; wood oil in

blends with other oils

Soluble in aliphatic or aliphaticaromatic solvent mixtures; good

drying characteristics, durability, and

gloss

Oxidizing


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3.1.2 Quy trnh sn xut

Alkyds c tng hp t phn ng trng ngng (polycondensation) ca

cc axit v ru cho n khi t c mi quan h ch s axit - nht

(viscosity) nh trc. P ng thng c thc hin di kh tr (inert

gas) hoc hi dung mi gim thiu phn ng oxidation ca cc thnh

phn bt bo ha (nh ni i). Trong giai on u ca phn ng, ch s

axit gim nhanh chng, v nht tng chm. Cng v sau ch s axit

gim chm. Quy trnh sn xut c th theo, phng php nng chy, hoc

bng cch s dng mt lng nh dung mi (mt hnh thc azeotrope vinc) (gi l phng php dung mi).

Hn na, trong cc vic chun b sn xut cc polyeste bin tnh vi axit

bo, hoc Triglyceride hoc cc acid bo c s dng nh l nguyn liu

ban u. Hai qu trnh ny c gi tt l QT monoglyceride hoc qu

trnh acid bo.


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So snh Phng php nng chy vi Phng php Dung mi

PP nng chy l phng php c nhng vn cn c s dng rng ri,

c bit l i vi du alkyds c hm lng du 60% hoc nhiu hn.Phn ng c thc hin ti nhit 220 n 250 C, di mi trng

kh tr, c s dng cho vic kh nc, nhng cng l nguyn nhn gy

mt polyols v ca phthalic anhydride.

Trong phng php dung mi, phn ng esterification c thc hin

trong s hin din ca mt s lng nh nc (khng tan)-dung mi,

thng l xylene. Qu trnh c thc hin lin tc km theo chng cng

ph ca cc dung mi. Cc xylene-hi nc l hn hp ngng t, nc

c tch bit vi dung mi v tr v cho thit b phn ng (reactor). Nhit phn ng c qun l bi nhit hon lu (refluxing) , ph thuc

vo s lng xylene s dng, 5% l c gi tr bnh thng. Nhn chung,

phng php dung mi kim sot tt hn cc sn phm resin, thnh phn,

v hu nh khng c thit hi v nguyn liu do qu trnh bay hi.

PP Monoglyceride so vi PP acid boKhi mt Triglyceride du c gia nhit vi polyols v polybasic axit, cc

polyols phn ng vi axit d dng, v to thnh mt hn hp ca

Triglyceride v polyeste khng bin tnh.

Cch khc phc vn ny l thc hin vic kim sot chuyn ha

este (transesterification) ca fatty acid trc khi bc sang phn ng

trng ngng (condensation). Vic ny thng c thc hin bng cch

phn ng ca 1 mole Triglyceride vi 2 moles ca glycerol (hoc mt

polyol) nhit 220 n 250 C cho n khi t c l giai on

monoglyceride. Catalysts c a thch PbO, Ca (OH) 2

Sau khi hnh thnh monoglycerides, cc axit polybasic v phn cn li ca

polyols ang c thm vo, v phn ng condensation c thc hin

cho n khi t c nht v ch s axit.


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Phng php acid bo s dng khng phi l Triglyceride m l cc

acid bo ca n. Song song vi vic la chn cc thnh phn polyol t

do hn, qu trnh ny cho lp li v kim sot trong sn xut tt hn

v trng lng phn t v phn b TLPT ca cc resin. Ngoi ra, qutrnh ny cho php phn ng condensation tin hnh tt hn (ch s acid

thp), lm thun li hn cho tnh cht kh.

S la chn qu trnh sn xut khng ch l vn tm phng php

tng hp ph hp nht. C khc bit r rt tnh cht mng phim alkyds

gia nhng alkyd c cng thnh phn, nhng khc nhau v phng

php tng hp.

3.1.4 Cac thong so ac trng cua nha alkyd

+ Loai dau: lanh, chu,u nanh( kho, ban kho)

+ Ham lng dau hoac acid beo %

+ Loai polyester (polyol ? polyacid ?, . . .)

+ Co dung moi hay khong? Loai nao? Ham lng ran?

+ Ty trong (tnh n pha che)

+ CA, COH, . . .

+ Ch so mau+ o nht.

+ Hng dan s dung : % chat lam kho, thi gian kho.

+ Lnh vc ng dung.


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ng dng

Alkyd resins l loi nha cho tnh bm dnh, tnh cht kh tt. Mng phim

c c t n c tnh mm do v bn thi tit (durability) tt. Bng

cc cch bin tnh khc nhau , mt s tnh cht c th c ci thin.

im yu ca alkyds l nhy cm vi qu trnh thy phn bi kim. Sau

y l m t s lc vi loi alkyd resins:

Alkyds Du botan trong dung mi hydrocarbon mch thng (aliphatic

solvents). Thng c p dng bng cch qut, chng c s dng

trong sn trang tr bn ngoi v sn tng, cng nh trong hng hi vbo v kim loi. Chng cng c s dng rng ri trong sn bng

khng mu.

Alkyds du trung bnhtan trong hn hp dung mi aliphatic varomatic. Loi kh trong khng kh c s dng cho cc ng dng

cng nghip xe, chng hn nh lp lt (primers) v lp bn trong

(undercoatings), sn cho kim loi. Cc loi khng b oxi ha

(nonoxidizing) thng c s dng nh l cht ha do trong sn

nitrocellulose.

Alkyds du gytan trong dung mi thm khng tan trong aliphatic. Loi

kh trong khng kh c s dng trong lp lt (ng rn nhit) (baking

primers) v sn men, bng mt mnh n hoc cng vi cc resins khc,

chng hn nh ur hoc melanine resins. Cc loi khng kh

(nondrying) ch yu c s dng trong sn nitrocellulose hoc kt hp

vi ur hoc melanine resins trong cc sn phm ng rn bng nhit

v bng axit.


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3.1.5 Mot so alkyd bien tnh tieu bieu:

+ Vinyl hoa nha Alkyd.

+ Uralkyd


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+ Epoxy Ester

3.2 Nha Polyester bao hoa khong dau.


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Polyester resins, ging nh nha alkyds, l sn phm ca phn ngesterification ca di-hoc polyhydric Alcohol vi di-hoc poly- axit hocanhydrides.

Tuy nhin trong thc t, c nhiu phc tp hn, c nhiu loi alcohol v acidkhc nhau c s dng tng nha polyester.Khng ging nh alkyd, khng c s bin tnh bng acid bo, v cu trc canha n gin hn. i khi di-axit aliphatic mch di nh azelaic acid vsebacic axit c th c s dng trong mt s cc cng thc polyester, ccaxit carboxylic (khng ging nh hu ht cc acid bo) khng c cha ni ilin hp hoc khng lin hp.

Do Polyesters khng hnh thnh mng phim bng c ch oxi ha(oxidative), y cng l im khc bit ca n i vi tt c alkyds lm khbng khng kh.

Trn thc t, Polyester resins l cht to mng chuyn i ha hc. ctnh ng rn (ni mng) ty thuc vo tnh cht ca cc nhm chc hotng cn li ca n. Nha polyesters c th chia lm 2 loi: polyesters (boha) saturated, l Polymers mch thng, mach nhnh, mch vng c mangnhm carboxyl, hoc hydroxyl nhng khng c bt bo ha (ni i); vunsaturated polytesters c cu trc tng t, nhng c bit l trong mngcn nhng ni i bt bo ha c th to mng (crossling) nh gc t do.

Saturated polyesters hnh thnh mng nh phn ng condensationpolymerization vi cc loi nha khch nh nha amino formaldehyde,epoxies, hoc polyisocyanates c cha cc nhm hot ng. Cc nhmhot ng trn saturated polyesters c th l mt trong hai nhm hydroxyl

hoc nhm carboxylic axit (tu thuc vo thit k qu trnh tng hp v t lcc thnh phn c bn (acid, alcohol)).

Tu thuc vo polyme hnh thnh,cc nhm cn li trn polymer v ccnhm hot ng ca cht khu mng (cross linker), chuyn haca ccsaturated polyester c th xy ra nhit thng hoc nhit cao.


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To mng nhit thng, h to mng hai thnh phn. nhit cao,

cc resins c th c trn ln li vi nhau. V d hnh thnh urethanes

vi polyisocyanates (qua nhm hydroxyls) l mt phn ng nhit phng.

Chuyn i cc amino resins (bng hydroxyl polyester), cc epoxy resins(bng carboxylated resin) l chuyn i nhit cao.

Cha kha tng hp resin l t l cc monomer. Thng dng nht, mt

lng tha polyol c s dng, cho nha c tha nhm hydroxyl

(thng cui mch).Trng hp cn c carboxylated polymer, dng lng

tha axit.

3.2.1 Nguyen lieu: Polyols va Polyacid thong dung

Alcohol FunctionalityEquivalent

Weight

Ethylene glycol (EG) 2 31

1.6-Hexanediol (HD) 2 59

Neopentyl glycol (NPG) 2 52

Diethylene glycol (DEC) 2 53

Triethylene glycol (TEG) 2 75

Bisphenol A (BA) 2 114

Trimethylol ethane (TME) 3 40

Trimethylol propane (TMP) 3 44,7

Pentaerythritol (Penta) 4 34


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Acid FunctionalityEquivalent

Weight

Benzoic acid 1* 122

Succinic acid 2 59

Adipic acid 2 73

Phthalic anhydride (PA) 2 72

Isophthalic acid (IPA) 2 83

Terephthalic acid (TA) 2 83

Trimellitic acid 3 70

Trimellitic anhydride (TMA) 3 64

*Used as a chain terminator


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Classification of Saturated PolyestersSaturated polyesters for use as binders in paints and coatings may be

classified according to their molecular weight and their functionality. High

molecular weight polyesters are predominantly linear, thermoplastic

polymers with molecular weights from 10,000 to 30,000. Generally, they

are copolyesters containing terephthalic and/or isophthalic acid and

aliphatic diacids and a blend of diols. In contrast to terephthalic acid

homopolyesters, they exhibit better solubility in solvents.

In coatings, they impart a high degree of flexibility paired with excellent

surface hardness and stability. High molecular weight linear polyesters

may be used as physically drying binder components in paints, although

the majority of uses are in baking enamels for highly flexible coatings,

such as coil and can coatings in combination with amino resins or other

suitable hydroxyl-reactive cross-linkers. Certain special grades of high

molecular weight polyesters are ground and used as thermoplastic

powder coatings.


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Low molecular weight polyesters range from 500 to 7000 and are, in

general, not suitable as physically drying binders. Because of their low

degree of polymerization, they carry a great many functional terminal

groups. Low molecular weight polyesters may be linear or branched; byvariation of the manufacturing process, it is possible to incorporate mostly

either hydroxyl or carboxyl end groups, or both kinds.

By themselves, low molecular weight polyesters are not satisfactory film

formers. They require a reaction partner capable of reacting with the end

groups of the polyester and causing the formation of a cross-linked,

duroplastic film. Amino resins and polyisocyanates are suitable as such

cross-linking agents for hydroxyl polyesters, whereas epoxy resins and

polyoxazolins may be used for carboxyl polyesters. By proper selection of

the reactants, the formulator can design products ranging from two-component or one-pack solvent-borne enamels with amino resins or

blocked polyisocyanates to powder coatings or, via the salt formation of

carboxyl polyesters, water-soluble stoving paints.

By reacting the native terminal groups of polyesters (i.e., hydroxyls orcarboxyls) with at least bifunctional monomers or oligomers, saturated

polyesters may be further modified in many ways.

Solubility

Naturally, chemical composition will be the dominant factor in

determining the solubility of a polyester; however, this dominance may be

exhibited either directly or indirectly (by affecting the morphology). The

solubility of polyesters decreases rapidly with increasing crystallinity.

Highly crystalline copolyesters are insoluble in many common solvents.

They can be dissolved only in blends of phenol and o-dichlorobenzene at

higher temperatures. Polyesters of medium crystallinity are soluble in

methylene chloride; weakly crystalline polyesters will also dissolve inaromatic hydrocarbons, such as toluene.

Amorphous polyesters will dissolve in a variety of polar solvents,

such as esters, etheresters, ketones, and aromatic and chlorinated

hydrocarbons.

Within the amorphous polyesters, chemical composition will have a

direct effect on solubility. Thus, shifting the glycol ratio in a polyester from

ethylene glycol toward neopentyl glycol will enhance the solubility of the

resulting polyester.


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Chemical Properties

Polyesters all contain the hydrolytically unstable ester linkage, the

chemical resistance of saturated polyesters is much superior to their alkyd

cousins. Alkyds are severely compromised in this respect by the presence

of the triglyceride. So improved are the resistance properties of thesaturated polyesters (and, more particularly, the unsaturated polyesters

discussed below) compared to alkyds that they have found wide uses in

highly chemical-resistant systems for severe exposures.

Generally speaking, polyesters have excellent stability toward light,

oxygen, water, and many chemicals. The weakest spot in the polymer

chain is the ester group, with its potential sensitivity to hydrolysis.

Accordingly, degradation may occur, provided there is an environment that

combines moisture with acids or alkali or other catalytically active

materials, plus the possibility for the moisture to permeate into the

polyester.

Chemical resistance can be upgraded by the selection of the cross linking

resin and the design and functionality of the resin itself. For example, if the

polyol of the polyester is selected so that it has no hydrogens on the

carbon atom that is "beta to" (or once removed from) the hydroxyl, then the

resultant ester is more hydrolytically stable.

Similarly, the light stability, exterior durability, and heat resistance of a

formulation may be optimized by the selection of components. Aromaticpolyols such as bisphenol A may improve heat resistance, but the aliphatic

materials are preferred for light stability and durability.

There is much opportunity for property design and custom tailoring through

molecular engineering in the synthesis of polyesters. Perhaps even more

opportunity exists when molecular engineering is used by the coatings

chemist in the final use of the polyester in the coating formulation.

The effect of the design of the cross linker and its combination with the

polyester will also have a great effect on the final properties of the coating.

Triglycidyl isocyanurate-cured systems will, for example, give far better

exterior durability in powder coatings than will the use of the more

conventional bisphenol A-based epoxies (Fig. 13-4). Again, using the same

polyester, excellent exterior two-pack urethanes will be produced using

hexamethylene di-isocyanate-based cross linkers (Fig. 13-5). Toluene di-

isocyanate cross linkers will, conversely, produce very poor exterior

systems, but these systems will have better heat and chemical resistance.


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Properties and Applications

Polyester coatings, especially cross-linked ones, exhibit excellent flexibility

or even elasticity, and they show very good impact, scratch, and stain

resistance. Their good adhesion properties, especially to metals, combined

with good corrosion protection and weather resistance, have made them

indispensable in a number of fields.

Application and markets for saturated polyesters are varied and extensive.

In the automotive industry, they are used as anti-chip surfacers over

cathodic electro-deposited primers and as colored base coat vehicles for

base coat/clear coat metallics. Here, the inherent toughness and flexibility

of the polyester is valued. These systems are cured with the melamine

cross linkers and often modified with cellulose acetate butyrate to maintain

flow properties. Polyester melamines are also used on trim components

and auto accessories.

Other applications include appliance coatings, flexible can coatings (insideand out) for food and beverage containers, and coatings for metal furniture

and light fixtures. Polyester coatings, especially siliconized polyester coil

coatings for exterior metal siding, benefit from the exceptional durability

and excellent flexibility of these resins, which help resist the effects of post

cure forming operations.

Two-pack, ambient-cured urethanes based on polyesters cured with

hexamethylene diisocyanate and, to a lesser extent, isophorone

diisocyanate-based cross linkers are now used extensively as high

performance maintenance finish coats for structural steel.They are often

employed over intermediate coats based on epoxies and aromatic

urethanes and zinc-rich primers based on organic and inorganic vehicles.


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Carboxylated polyester reactions with epoxy systems


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3.3 Polyester khong no bat bao hoa

Acid RemarksMaleic anhydride

Employed as an acid and a source ofunsaturation in unsaturated polyesters

Fumaric acid Employed as an acid and a source of

unsaturation in unsaturated polyesters


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Application and Properties of Unsaturated Polyesters

Unsaturated polyesters have very large markets in non-coating

applications, such as laminates, encapsulants. press mold applications, and

hand lay-ups, particularly when used in combination with fiberglass

reinforcement. Pleasure boats, bathroom fixtures, swimming pools,

translucent panels and tanks, piping, drip pans, and other equipment (for the

chemical, plating, and photographic industries especially) are fabricated

from unsaturated polyesters.

As coating and lining materials, unsaturated polyesters are typified by

systems having high gloss, fast cure, short pot life, and very high build

capabilities. The coatings are generally hard and very impact resistant. They

are not flexible systems, and a high volume shrinkage on polymerization

may result in poor adhesion unless good surface preparation and suitable

primers are employed. Chemical resistances are very good in spite of the

ester group. As is noted with the saturated polyesters, optimum chemical

resistance may be designed into these systems by the selection of the

ingredientsiso- or terephthalic acids, bisphenol A, and NPG-based

ol ols.

In coatings, the largest polyester applications are as radiation curing

systems in furniture and wood finishing. Large volumes are also

consumed as gel coats (polyester coatings sprayed onto molds) for boats

and bathroom fixtures and in two-pack automotive refinish applications

(including fillers and putties).

Documents

Chuong 3 Alkyd+Polyester VN N