High solids polyester polyols

The present invention is directed to a polyester polyol having a molecular weight between about 850 and 2000, a functionality of about 5 to 9 and an OH number of about 200 to 350, based on 100% solids, which is prepared by reacting PA1 (a) an acid component based on at least one polyfunctional cycloaliphatic or aromatic carboxylic acid, anhydride or ester and optionally up to about 50 percent by weight of at least one acyclic, polyfunctional carboxylic acid and PA1 (b) a hydroxyl component containing at least a portion of at least one polyol having a functionality of at least 3. The present invention is also directed to a process for preparing these polyester polyols by reacting the above components and is further directed to the use of these polyester polyols in combination with organic polyisocyanates for the production of polyurethanes, particularly polyurethane coatings.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to polyester polyols which have a low 
viscosity so that they may be formulated at high solids contents for use 
in the preparation of polyurethanes, particularly polyurethane coatings. 
2. Description of the Prior Art 
It is known to use polyester polyols for the production of hard, flexible 
polyurethane coatings having good acid and chemical resistance, gloss 
retention and abrasion resistance as well as light stability when 
(cyclo)aliphatic polyisocyanates are used as co-reactants. In order to 
obtain these properties highly branched polyester polyols are reacted with 
the organic polyisocyanates. However, due to the high degree of branching, 
the polyester polyols have a high viscosity and considerable amounts of 
solvent must be used to reduce the viscosity of the polyester polyols to 
an acceptable level, especially if the coatings are applied in a spray 
application. Because the use of large amounts of solvent may create 
environmental difficulties, particularly in a spray application, there is 
a need for polyester polyols which have a lower viscosity so that they may 
be formulated with less solvent than with previously known polyester 
polyols. It is also important to maintain the coatings properties obtained 
from the highly branched polyester polyols. 
Accordingly, it is an object of the present invention to provide low 
viscosity polyester polyols which may be formulated at high solids 
contents than previously known polyester polyols such that the polyester 
polyols may be used in spray applications. It is also an object of the 
present invention to provide polyester polyols which may be used to 
produce polyurethane coatings which maintain the level of coatings 
properties obtained from the previously known polyester polyols, i.e. good 
acid and chemical resistance, gloss retention, abrasion resistance and 
light stability. Surprisingly, these objects may be achieved by using the 
polyester polyols of the present invention set forth hereinafter. 
SUMMARY OF THE INVENTION 
The present invention is directed to a polyester polyol having a molecular 
weight between about 850 and 2000, a functionality of about 5 to 9 and an 
OH number of about 200 to 350, based on 100% solids, which is prepared by 
reacting 
(a) an acid component based on at least one polyfunctional cycloaliphatic 
or aromatic carboxylic acid, anhydride or ester and optionally up to about 
50 percent by weight of at least one acyclic, polyfunctional carboxylic 
acid and 
(b) a hydroxyl component containing at least a portion of at least one 
polyol having a functionality of at least 3. 
The present invention is also directed to a process for preparing these 
polyester polyols by reacting the above components and is further directed 
to the use of these polyester polyols in combination with organic 
polyisocyanates for the production of polyurethanes, particularly 
polyurethane coatings. 
DETAILED DESCRIPTION OF THE INVENTION 
It was very unexpected that the polyester polyols according to the 
invention which have a lower viscosity and functionality than previously 
known polyester polyols could be used for producing polyurethane coatings 
which have properties which are not substantially different from coatings 
prepared with the higher viscosity and functionality polyester polyols 
known in the industry. This is especially surprising with regard to the 
solvent resistance which is dependent upon the crosslink density which in 
turn is directly related to the functionality or amount of branching of 
the polyester polyol. 
The polyester polyols generally have a molecular weight of about 850 to 
2000, preferably about 1000 to 1700; a functionality of about 5 to 9, 
preferably about 6 to 8; and an OH number of about 200 to 350, preferably 
about 230 to 330 and most preferably about 250 to 300, based on 100% 
solids. The polyester polyols may be prepared by reacting polybasic, 
generally dibasic carboxylic acids with polyols wherein at least a portion 
of the polyols have a functionality of at least 3. In the preparation of 
the polyester polyols it is possible to use the corresponding 
polycarboxylic acid anhydrides or polycarboxylic acid esters of lower 
alcohols instead of the free polycarboxylic acids. 
Suitable aromatic or cycloaliphatic polycarboxylic acids for preparing the 
polyester polyols include phthalic acid, isophthalic acid, terephthalic 
acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, 
hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, 
endomethylene tetrahydrophthalic acid anhydride, tetrahydroisophthalic 
acid, hexahydroisophthalic acid, tetrahydrophthalic acid, 
hexahydrophthalic acid, tetrahydroterephthalic acid, hexahydroterephthalic 
acid, dimethylterephthalate and bis-glycolterephthalate. 
In addition to the aromic or cycloaliphatic polycarboxylic acids, which 
should be used in a quantity of at least about 50 percent by weight, 
preferably at least about 60 percent by weight, of the acid component of 
the polyester, it is also possible to use acyclic polycarboxylic acids 
such as succinic acid, succinic acid anhydride, adipic acid, suberic acid, 
azelaic acid, sebacic acid, glutaric acid, malonic acid and unsaturated 
acids such as maleic acid, maleic acid anhydride or fumaric acid. The 
previously described polycarboxylic acids may be unsaturated or they may 
be substituted, e.g. by halogen atoms. In addition to the dicarboxylic 
acids previously described, it is also possible to use polyfunctional 
carboxylic acids such as trimellitic acid or trimellitic acid anhydride in 
order to provide branching in the polyester polyol. However, it is 
preferred to introduce branching through the polyol component used to 
prepare the polyester polyol. Further, it is also possible to use 
monocarboxylic acids such as 2-ethylhexanoic acid to control the 
functionality. 
The low molecular weight polyol reaction partner for use in preparing the 
polyester polyols include the low molecular weight chain extenders known 
from polyurethane chemistry. It is preferred to introduce the branching 
into the polyester polyols by using low molecular weight polyols having a 
functionality of at least 3 as at least a portion of the hydroxyl 
component. Suitable polyfunctional chain extenders include trimethylol 
propane-(1,1,1), glycerol, hexanetriol-(1,2,6), butanetriol-(1,2,4), 
trimethylolethane-(1,1,1), pentaerythritol, mannitol, sorbitol, methyl 
glycoside, sucrose, and 1,1,2- or 1,1,1-tris-(hydroxyphenyl)-ethane. 
Low molecular weight diols and monoalcohols may be blended with the higher 
functional polyols in order to achieve the desired functionality. Suitable 
diols include ethylene glycol, propylene glycol-(1,2) and -(1,3), butylene 
glycol-(1,4), -(1,3), and -(2,3), hexanediol-(1,6), octanediol-(1,8), 
neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane) 
and 2-methyl-1,3-propanediol. As in the case of monocarboxylic acids, it 
is also possible to use monoalcohols such as methanol, ethanol, propanol, 
butanol, 2-ethylhexanol, etc., in minor quantitites to control the 
functionality. 
The molar proportions of polyols and polycarboxylic acids employed are such 
that there is an excess of hydroxyl groups over the number of carboxylic 
acid groups. 
The functionality (f.sub.OH) may be determined by the following formula 
##EQU1## 
For example, if two moles of a glycol (4 OH equivalents), 2 moles of a 
triol (6 OH equivalents) and three moles of a diacid (6 acid equivalents) 
are reacted to form a polyester polyol, then the theoretical average 
functionality is four. When monofunctional acid is used to reduce the 
functionality, the above formula may still be used. Thus, if one mole of a 
monocarboxylic acid (1 acid equivalent) is added to the above ingredients, 
the theoretical average functionality is three. By varying the amounts and 
functionalities of the individual components, polyester polyols with 
virtually any theoretical average functionality may be obtained. 
The reaction between the glycol and the acid is carried out under normal 
esterification conditions well known and described in the prior art; see 
for example Polyurethanes: Chemistry and Technology, Part I, pages 45-46, 
1962, J. H. Saunders and K. C. Frisch, John Wiley & Sons, New York, N.Y. 
Illustratively, the esterification is conducted in the absence of solvent 
under a flow of nitrogen and at temperatures of about 150.degree. C. to 
250.degree. C., preferably about 190.degree. C. to 225.degree. C. for a 
period of about 4 to 40 hours, preferably about 6 to 24 hours. The 
reaction is terminated when the acid number of the product is less than 
about 4, preferably less than about 2. Water of condensation which is 
formed as a by-product during the reaction may be removed by conducting 
the reaction under vacuum conditions. 
While catalysts are not necessary, they may be employed to shorten the 
esterification period. Suitable catalysts include p-toluene-sulfonic acid, 
magnesium oxide, calcium oxide, antimony oxide, zinc oxide, lead oxide, 
magnesium acetate, calcium acetate, zinc acetate, lead acetate, sodium 
acetate, potassium acetate, sodium 2-ethylhexanoate, potassium 
2-ethylhexanoate, various organic amines, sodium methoxide, potassium 
methoxide, sodium alkoxytitanates, tetraalkyl titanates, hydrated 
monobutyl tin oxide, stannous oxalate, stannous chloride dihydrate and the 
like. 
In order to prepare the two component polyurethane coating compositions, 
the polyester polyols are blended and reacted with suitable organic 
polyisocyanates known from polyurethane chemistry. The organic 
polyisocyanate may be monomeric in nature or polyisocyanate adducts 
prepared from monomeric polyisocyanates, preferably diisocyanates, and 
containing biuret, allophanate, urea, urethane or carbodiimide groups or 
isocyanurate rings. Suitable isocyanates and methods for preparing the 
polyisocyanate adducts are set forth in U.S. Pat. No. 4,439,593 herein 
incorporated by reference. The polyisocyanate adducts are preferably used 
to prepare the coatings especially when the coatings are applied by spray 
applications, due to their lower vapor pressure. 
Preferred polyisocyanate adducts are biuret group-containing 
polyisocyanates based on 1,6-diisocyanatohexane and polyisocyanate adducts 
containing isocyanurate groups and based on 2,4-diisocyanatotoluene and/or 
2,6-diisocyanatotoluene, 1,6-diisocyanatohexane, isophorone diisocyanate 
and mixtures of these diisocyanates. Also preferred are polyisocyanate 
adducts containing urethane groups and based on trimethylol propane and 
2,4-diisocyanatotoluene and/or 2,6-diisocyanatotoluene, 
1,6-diisocyanatohexane, isophorone diisocyanate and mixtures of the 
diisocyanates. The most preferred polyisocyanate adducts are the biuret 
group-containing polyisocyanates based on 1,6-diisocyanatohexane, 
polyisocyanate adducts containing isocyanurate groups and based on 
1,6-diisocyanatohexane and polyisocyanate adducts containing urethane 
groups based on trimethylolpropane and isomeric mixtures of 
diisocyanatotoluene. The former two most preferred polyisocyanate adducts 
are especially preferred when resistance to yellowing under the effect of 
ultraviolet light is required. Mixtures may also be used, especially 
mixtures of the biuret group-containing polyisocyanates based on 
1,6-diisocyanatohexane and the polyisocyanate adducts containing 
isocyanurate groups and based on 1,6-diisocyanatohexane as set forth in 
copending application, U.S. Ser. No. 738,909, filed Dec. 8, 1986. 
In addition to the polyester polyols and the polyisocyanates, the coating 
composition may also contain solvents, catalysts, pigments, dyes, 
levelling agents, and the like which are well known in the field of 
polyurethane chemistry. 
Even though the compositions according to the present invention require 
less solvent than those of the prior art to achieve a suitable processing 
viscosity, especially when used in spray applications, solvents may be 
added to the systems to further reduce their viscosity. Suitable solvents 
include the known polyurethane solvents such as toluene, xylene, 
butylacetate, ethylacetate, ethylene glycol monoethyl ether acetate, 
ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether 
acetate, ethylene glycol monohexyl ether acetate, propylene glycol 
monomethyl ether acetate, diethylene glycol monoethyl ether acetate, 
diethlyene glycol monobutyl ether acetate, methyl ethyl ketone, methyl 
isobutyl ketone, methyl amyl ketone, hydrocarbon solvents such as hexane 
and heptane, aromatic solvents and also mixtures of these solvents. 
Suitable polyurethane catalysts include those known in polyurethane 
chemistry such as tertiary amines, quaternary ammonium hydroxides, alkali 
metal hydroxides, alkali metal alcoholates, alkali metal phenolates and, 
in particular, organic tin compounds. The catalysts are generally used in 
a quantity of about 0.001 to 10 percent by weight, based on the quantity 
of polyesters used according to the invention. 
Suitable pigments include the known inorganic and organic pigments and 
dyes, particularly inorganic pigments such as iron oxide, carbon black and 
titanium dioxide. 
The coatings according to the invention may be applied by any of the known, 
conventional methods such as roller, brush or immersion, especially spray 
gun or airless spray gun. 
The invention is further illustrated but is not intended to be limited by 
the following examples in which all parts and percentages are by weight 
unless otherwise specified.

EXAMPLES 
The following components were used in the examples: 
Polyisocyanate A--an isocyanurate group-containing polyisocyanate having an 
equivalent weight of 216, prepared by trimerizing hexamethylene 
diisocyanate and present at 90% solids in a mixture of equal parts n-butyl 
acetate and solvent naphtha 100 (available as Desmodur N 3390 from Mobay 
Corporation). 
Polyisocyanate B--a biuret group-containing polyisocyanate based on 
hexamethylene diisocyanate and having an equivalent weight of 183 
(available as Desmodur N 3200 from Mobay Corporation). 
Polyisocyanate C--a urethane group-containing polyisocyanate prepared from 
toluene diisocyanate and trimethylol propane (available as Mondur CB-75 
from Mobay Corporation). 
The following polyester polyols were prepared by charging the reactants to 
a closed reaction vessel while maintaining a nitrogen blanket. The 
reactants were heated to 210.degree. C. and reacted at atmospheric 
pressure until about 80% of the theoretical water has been collected. At 
that time the pressure was reduced to a level of about 10 to 15 mm Hg. The 
reaction was maintained under these conditions until the acid number was 
reduced to a value of less than 2 mg KOH/g at 100% solids. After 
completion of the reaction, the reactants were cooled and during this step 
the solvent was added. All of the equivalent weights and OH numbers set 
forth are based on 100% solids. 
Polyol A--a polyester polyol present as a 75% solids solution in propylene 
glycol monomethyl ether acetate, having an equivalent weight of about 195, 
an OH number of about 288 and a functionality of about 6.4, and prepared 
from 
47.0 parts 2-ethylhexanoic acid 
409.8 parts trimethylol propane 
239.6 parts phthalic acid anhydride and 
119.8 parts adipic acid. 
Polyol B--a polyester polyol present as an 80% solids solution in propylene 
glycol monomethyl ether acetate, having an equivalent weight of about 200, 
an OH number of about 280 and a functionality of about 6.4, and prepared 
from the same reactants and amounts as Polyol A. 
Polyol C--a commercially available polyester polyol present as a 65% solids 
solution in proplyene glycol monomethyl ether acetate, having an 
equivalent weight of about 215, an OH number of about 260 and a 
functionality of about 12-12.5, and prepared from trimethylol propane and 
phthalic acid anhydride. 
Polyol D--a commercially available polyester polyol present as a 65% solids 
solution in propylene glycol monomethyl ether acetate, having an 
equivalent weight of about 215, an OH number of about 260 and a 
functionality of about 12-12.5, and prepared from trimethylol propane, 
hexahydrophthalic acid anhydride and phthalic acid anhydride. 
Additive A--a 33% solution in a 1:1 mixture of methyl ethyl ketone and 
propylene glycol monomethyl ether acetate of a cellulose acetate/butyrate 
flow aid (available as CAB-551-0.1 sec from Eastman Chemical). 
Additive B--a 10% solution in propylene glycol monomethyl ether acetate of 
a fluorocarbon surfactant (available as FC-430 from 3M Company). 
Additive C--a 50% solution in a proprietary solvent of a wetting and 
suspending agent based on the salt of a long chain polyaminoamide and a 
high molecular weight acid ester (available as Antiterra U from Byk 
Chemie). 
Additive D--a hindered amine light stabilizer (available as Tinuvin 292 
from Ciba-Geigy). 
Additive E--a benzotriazole light stabilizer (available as Tinuvin 1130 
from Ciba-Geigy). 
Catalyst A--a 1% solution in propylene glycol monomethyl ether acetate of 
dibutyl tin dilaurate (available as T-12 from Air Products and Chemicals). 
Catalyst B--a 1% solution in a 1:1 mixture of propylene glycol monomethyl 
ether acetate and methyl ethyl ketone of dibutyl tin dilaurate (available 
as T-12 from Air Products and Chemicals. 
Solvent Blend A--a blend of 40 parts propylene glycol monomethyl ether 
acetate, 10 parts n-butyl acetate, 40 parts methyl ethyl ketone and 10 
parts xylene. 
Solvent Blend B--a blend of equal parts methyl amyl ketone, methyl isobutyl 
ketone and methyl n-propyl ketone. 
EXAMPLE 1 
A pigmented polyol composition was prepared by mixing the following: 
1200.0 parts of Polyol A 
1415.3 parts TiO.sub.2 
105.0 parts Additive A 
16.0 parts Additive B 
9.4 parts Additive C 
627.6 parts Solvent Blend A. 
153.8 parts of this polyol composition were mixed with 37.5 parts of 
Polyisocyanate A, 10.4 parts of Polyisocyanate B (NCO equivalent ratio 
75/25), 15.2 parts of Solvent Blend A and 0.6 parts of Catalyst A. This 
coating composition was sprayed onto steel panels using a Binks Model 18 
conventional air gun with a 66SF tip at 40 psi. An excellent coating was 
obtained which had good gloss and did not suffer from pigment 
flocculation. 
EXAMPLE 2 
A pigmented polyol composition was prepared from the following: 
1129.2 parts Polyol A 
1280.4 parts TiO.sub.2 
98.8 parts Additive A 
15.2 parts Additive B 
12.8 parts Additive C 
25.6 parts Additive D 
8.0 parts Additive E 
34.0 parts Catalyst B 
900.0 parts Solvent Blend A. 
150 parts of the pigmented polyol composition were mixed with 22.1 parts of 
Polyisocyanate A and 18.4 parts of Polyisocyanate B (NCO equivalent ratio 
50/50). The coating composition was applied to steel panels in the manner 
of Example 1. An excellent coating was obtained which had good gloss and 
did not suffer from pigment flocculation. 
EXAMPLE 3 
150 parts of the pigmented polyol composition of Example 2 were blended 
with a mixture of 33.1 parts of Polyisocyanate A and 9.2 parts of 
Polyisocyanate B (NCO equivalent ratio 75/25). The coated composition was 
applied to steel panels in the manner of Example 1. An excellent coating 
was obtained with good gloss which did not suffer from pigment 
flocculation. 
EXAMPLE 4 
A pigmented polyol composition was prepared by mixing the following: 
265.0 parts of Polyol B 
25.8 parts Additive A 
4.1 parts Catalyst B 
63.2 parts Solvent Blend B. 
100 parts of this polyol composition were mixed with 53.7 parts of 
Polyisocyanate B to form a coating composition having a solids content of 
75%. 
The viscosity of the coating composition was measured using a number 4 Ford 
Cup at various solid contents obtained by diluting the composition with 
Solvent Blend B. 
Viscosity at 
75% solids=5 minutes, 4 seconds 
71% solids=2 minutes, 55 seconds 
65% solids=1 minute, 12 seconds 
61% total solids=45 seconds 
A freshly prepared sample immediately diluted to 61% solids had a viscosity 
of 31 seconds. 
Films prepared from the coating composition had the following properties: 
Pencil hardness--2H 
Methyl ethyl ketone (MEK) double rubs--200 
Gardner impact (direct/reverse)--160/160 in-lbs. 
EXAMPLE 5 (Comparison) 
A polyol composition was prepared by mixing the following: 
362.2 parts Polyol D, 
25.8 parts Additive A, 
4.1 parts Catalyst B 
2.0 parts Solvent Blend B. 
100 parts of this polyol composition were mixed with 53.7 parts of 
Polyisocyanate B to form a coating composition having a solids content of 
75%. The viscosity of the coating composition was measured using a number 
4 Ford Cup at various solids contents obtained by diluting the coating 
composition with Solvent Blend B. 
Viscosity at 
75% solids =too viscous to measure 
65% solids =2 minutes, 33 seconds 
55% solids =32 seconds 
Films prepared from the coating composition were very hazy and had the 
following properties 
Pencil hardness =3-4H 
MEK double rubs =200 
Gardner impact =40/20 in-lbs. 
EXAMPLE 6 
A polyol composition was prepared by mixing the following: 
265 parts Polyol B 
26.4 parts Additive A 
4.1 parts Catalyst B 
44.5 parts Solvent Blend B. 
100 parts of this polyol composition were mixed with 67.6 parts of 
Polyisocyanate A to form a coating composition having a solids content of 
75%. The viscosity of the coating composition was measured using a number 
4 Ford Cup at various solids contents obtained by diluting the coating 
composition with Solvent Blend B. 
Viscosity at 
75% solids =4 minutes, 58 seconds 
71% solids =2 minutes, 29 seconds 
65% solids =56 seconds 
61% solids =35 seconds 
The viscosity at 61% solids of a freshly made sample was 28 seconds. 
Films prepared from the coating composition had the following properties: 
Pencil hardness =2H 
MEK double rubs =200 
Gardner Impact =120/100 in-lbs. 
EXAMPLE 7 (Comparison) 
A polyol composition was prepared by mixing the following: 
326.2 parts Polyol D 
26.4 parts Additive A 
4.1 parts Catalyst B. 
100 parts of this polyol composition were mixed with 64.4 parts of 
Polyisocyanate A to form a coating composition having a solids content of 
73%. The viscosity of the coating composition was measured using a number 
4 Ford Cup at various solids contents obtained by diluting the coating 
composition with Solvent Blend B. 
Viscosity at 
73% solids =too viscous to measure 
65% solids =2 minutes, 19 seconds 
55% solids =28 seconds. 
Films prepared from the coating composition were hazy and had the following 
properties: 
Pencil hardness =3-4H 
MEK double rubs =200 
Gardner impact =40/20 in-lbs. 
EXAMPLE 8 
A polyol composition was prepared by mixing the following: 
611.8 parts Polyol A 
61.2 parts Additive A 
12.2 parts Catalyst B. 
100 parts of this polyol composition were mixed with 67.1 parts of 
Polyisocyanate B to form a coating composition having a solids content of 
82%. The viscosity of the coating composition was measured using a number 
4 Ford Cup at various solvent contents obtained by diluting the coating 
composition with Solvent Blend B. 
Viscosity at 
75% solids =greater than 5 minutes 
65% solids =1 minute, 3 seconds 
55% solids =22 seconds 
EXAMPLE 9 (Comparison) 
A polyol composition was prepared by mixing the following: 
648 parts Polyol C 
64.8 parts Additive A 
13 parts Catalyst B. 
100 parts of this coating composition were mixed with 55.5 parts of 
Polyisocyanate B to form a coating composition having a solids content of 
75%. The viscosity of the coating composition was measured using a number 
4 Ford Cup at various solids contents obtained by diluting the coating 
composition with Solvent Blend B. 
Viscosity at 
74% solids =too viscous to measure 
65% solids =3 minutes, 42 seconds 
55% solids =44 seconds. 
EXAMPLE 10 
100 parts of the polyol composition set forth in Example 8 were mixed with 
79.1 parts of Polyisocyanate A to form a coating composition having a 
solids content of 78.7%. The viscosity of the coating composition was 
measured using a number 4 Ford Cup at various solids contents obtained by 
diluting the coating composition with Solvent Blend B. 
Viscosity at 
75% solids =4 minutes 
65% solids =47.6 seconds 
55% solids =19 seconds. 
EXAMPLE 11 (Comparison) 
100 parts of the polyol composition set forth in Example 9 were mixed with 
65.8 parts of Polyisocyanate A to form a coating composition having a 
solids content of 72.4%. The viscosity of the coating composition was 
measured using a number 4 Ford Cup at various solids contents obtained by 
diluting the coating composition with Solvent Blend B. 
Viscosity at 
72.4% solids =too viscous to measure 
65% solids =3 minutes, 20 seconds 
55% solids =31.4 seconds. 
Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.