A curable organopolysiloxane putty-like composition comprising an organopolysiloxane having at least two alkenyl groups in one molecule, an organohydrogenpolysiloxane having at least three .tbd.SiH groups, a catalytic amount of platinum or a platinum compound, and an inorganic filler. This composition further comprises an organopolysiloxane modified with an alkyl group directly bonded to silicon atoms and having from 7 to 30 carbon atoms whereby the modified organosiloxane serving as an oil properly exudes prior to curing but does not exude appreciably after the curing. The composition is suitable particularly for impressions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to an impression material and 
particularly, to a curable organopolysiloxane putty-like composition which 
is kept putty-like prior to curing by the action of an internal releasing 
agent. Once the composition has been cured, it becomes useful as an 
impression material without impeding an appearance or lowering the 
dimensional accuracy because of a reduced degree of bleeding of the 
internal release agent. The term "impression material" used herein is 
intended to mean one which is used, for example, in the dental field as 
the imprint of the teeth and surrounding tissues for use as a mold in 
making dentures, or one which is used to imprint the hand. As a matter of 
course, the putty-like composition may be applied not only as such an 
impression material, but also for identification and electric insulation. 
2. Description of the Prior Art 
A variety of curable organopolysiloxane compositions are known in the art. 
For impression materials, there have been widely used those compositions 
which comprise organopolysiloxanes having an alkenyl group and 
organohydogenpolysiloxanes having a hydrogen atom directly bonded to the 
silicon atom (.tbd.SiH group) and wherein these siloxane compounds are 
subjected to addition reaction in the presence of a platinum catalyst. 
Putty-like compositions ordinarily used are those which are obtained by 
internally adding aliphatic hydrocarbon release agents such as, for 
example, liquid paraffin and white vaseline to the composition of the 
above type, so that the ingredients do not attach to hands when mixing. 
The aliphatic hydrocarbon added as the release agent is allowed to bleed on 
the putty composition surface prior to curing. This is very advantageous 
from the viewpoint of handling in that when mixed or kneaded, the 
putty-like composition does not attach to hands. However, the aliphatic 
hydrocarbon is caused to gradually bleed out on the surface after the 
curing, presenting the problems that the appearance of the cured product 
is worsened and that the size of the cured product after impression 
differs from that of a matrix. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a curable organopolysiloxane 
putty-like composition which overcomes the disadvantages of the prior art. 
It is another object of the invention to provide a curable 
organopolysiloxane putty-like composition which comprises, as a release 
agent, an organopolysiloxane having a predetermined amount of a long-chain 
alkyl group or groups whereby good working properties are obtained without 
attachment of the composition to hands during handling and bleedout of the 
release agent after curing rarely takes place. 
The present invention provides a curable organopolysiloxane putty-like 
composition which comprises: (1) 100 parts by weight of an 
organopolysiloxane having at least two alkenyl groups in one molecule; (2) 
an organohydrogenpolysiloxane having at least three .tbd.SiH groups in one 
molecule wherein the hydrogen atoms are directly bonded to the respective 
silicon atoms and used in an amount sufficient to provide 0.5 to 5 times 
by mole of the .tbd.SiH groups relative to the alkenyl groups in the 
ingredient (1); (3) a catalytic amount of platinum or a platinum compound; 
and (4) from 20 to 600 parts by weight of an inorganic filler. The present 
invention is characterized in that the putty-like composition further 
comprises, as ingredient (5), from 5 to 60 parts by weight of an 
organopolysiloxane having from 5 mole % to 50 mole % of alkyl groups 
having from 7 to 30 carbon atoms based on the total organic groups bonded 
to silicon atoms. 
The composition comprising the above ingredients (1) to (4) is a known 
addition reaction-type curable organopolysiloxane composition. It has been 
found that when the ingredient (5) which is a specific type of 
organopolysiloxane is added to the known composition as an internal 
release agent, this release agent is allowed to bleed out on the surface 
of the composition prior to curing and little bleedout on the surface 
occurs after the curing.

DETAILED DESCRIPTION AND EMBODIMENTS OF THE INVENTION 
The first ingredient used in the composition of the invention is an 
organopolysiloxane which should have at least two alkenyl groups each 
bonded to a silicon atom in one molecule. Such organopolysiloxanes are, 
for example, those of the following formulae 
##STR1## 
wherein R.sup.1 's may be the same or different and represent an 
unsubstituted or substituted monovalent hydrocarbon group, and R.sup.2 's 
may be the same or different and represent an alkenyl group having from 2 
to 4 carbon atoms, m is an integer of from 50 to 100,000, and n is an 
integer of from 0 to 10,000 provided that n/m=0 to 0.1. 
The unsubstituted or substituted monovalent hydrocarbon group represented 
by R.sup.1 includes an alkyl group having from 1 to 6 carbon atoms, e.g. a 
methyl group, an ethyl group, a propyl group, a butyl group or the like, 
an aryl group such as a phenyl group, a tolyl group or the like, or a 
substituted alkyl or aryl group wherein part or all of the hydrogen atoms 
of the above groups are substituted with a halogen atom, e.g. a 
chloromethyl group, a 3,3,3-trifluoropropyl group or the like. Of these, 
R.sup.1 is preferably an alkyl group having from 1 to 4 carbon atoms. More 
preferably, at least 50 mole % of the total of R.sup.1 's should be a 
methyl group. 
Examples of the alkenyl group represented by R.sup.2 include a vinyl group, 
an allyl group, a butenyl group and the like. 
The organohydrogenpolysiloxane used as the second ingredient acts, as a 
crosslinking agent, on the first organopolysiloxane ingredient and should 
have at least three hydrogen atoms directly bonded to the respective 
silicon atoms (.tbd.SiH groups) in the molecule. The 
organohydrogenpolysiloxane is of the following average unit formula 
EQU H.sub.a R.sub.b.sup.1 SiO.sub.[4-(a+b)]/2 
wherein R.sup.1 has the same meaning as defined with respect to the first 
ingredient, 0.01.ltoreq.a.ltoreq.1, preferably 0.02.ltoreq.a&lt;1, and 
1.6.ltoreq.b.ltoreq.2, preferably 1.8.ltoreq.b.ltoreq.2, provided that 
1.8.ltoreq.a+b&lt;3, preferably 1.95.ltoreq.a+b.ltoreq.2.95. Moreover, the 
organohydrogenpolysiloxane should preferably have from 3 to 500, 
preferably from 3 to 300 silicon atoms in the molecule and may be linear, 
branched or cyclic in structure. 
In order to permit good miscibility with the first ingredient, the second 
ingredient should preferably have a molecular weight lower than the first 
ingredient. The organopolysiloxane is used in such a way that the .tbd.SiH 
groups are provided in amounts of 0.5 to 5 times by mole the alkenyl 
groups in the first organopolysiloxane ingredient. If the amount is less 
than 0.5 times by mole, the addition reaction does not proceed 
satisfactorily. On the other hand, if the amount is over 5 times by mole, 
the resultant product becomes brittle and excess .tbd.SiH groups will be 
left in the final product, causing the product to be degraded as time 
passes. 
The third ingredient is platinum or a platinum compound which may be any 
known compound ordinarily used as a catalyst for the addition reaction. 
Examples of the third ingredient include platinum black or platinum 
supported on silica, carbon black or the like, chloroplatinic acid, an 
alcohol solution of chloroplatinic acid, complex salts of chloroplatinic 
acid, olefins and vinylsiloxane, and the like. The amount is preferably in 
the range of from 0.0001 to 0.1 part by weight per 100 parts by weight of 
the total of the first and second ingredients. 
The inorganic filler used as the fourth ingredient may be any material 
ordinarily used for this type of organopolysiloxane composition. Examples 
of such material include finely divided silica such as fumed silica, 
precipitated silica and the like, quartz powder, glass fibers, carbon 
powder, iron oxide, titanium oxide, zinc oxide, calcium carbonate, 
magnesium carbonate and the like. The amount of the inorganic filler is in 
the range of from 20 to 600 parts by weight, preferably from 50 to 400 
parts by weight, per 100 parts by weight of the first ingredient of the 
alkenyl group-containing organopolysiloxane. If the amount is less than 20 
parts by weight, the resultant putty-like composition becomes so soft that 
it is difficult to handle. If the amount is over 600 parts by weight, the 
composition becomes too hard to handle as well. 
The fifth ingredient is an organopolysiloxane which is added as an internal 
release agent. This compound should have from 5 to 50 mole %, preferably 
from 10 to 50 mole %, of alkyl groups having from 7 to 30 carbon atoms, 
preferably from 8 to 18 carbon atoms, based on the total of organic groups 
bonded to the silicon atoms. Preferably, the organopolysiloxane is a 
linear diorganopolysiloxane. Preferable examples include those compounds 
of the following formulae 
##STR2## 
In the above formulae, R.sup.3 and R.sup.4 have, respectively, the same 
meanings as R.sup.1 and R.sup.2 defined in the first ingredient, R.sup.5 
represents an alkyl group having from 7 to 30 carbon atoms, a is an 
integer wherein 0.ltoreq.a&lt;10,000, preferably 1.ltoreq.a&lt;5,000, b and c 
are, respectively, an integer wherein 1.ltoreq.b&lt;10,000, 0.ltoreq.c&lt;10,000 
and 1.ltoreq.b+c&lt;10,000 provided that 0.ltoreq.c/b&lt;9, d is an integer 
wherein 1.ltoreq.d&lt;10,000, preferably 1.ltoreq.d&lt;5,000, and e and f are, 
respectively, an integer wherein 1.ltoreq.e&lt;10,000, 0.ltoreq.f&lt;10,000 and 
1.ltoreq.e+f&lt;10,000 provided that 0.ltoreq.f/e&lt;9. R.sup.3 's and R.sup.4 
's may be, respectively, the same or different. Preferably, each R.sup.3 
is a methyl group, and each R.sup.3 is a methyl group and each R.sup.4 is 
a vinyl group. Moreover, it is also preferred that each R.sup.3 is a 
methyl group, each R.sup.4 is a vinyl group, and R.sup.5 is an alkyl group 
having from 8 to 18 carbon atoms in the respective formulae. 
More preferably, those compounds of the following formulae are used as the 
fifth ingredient 
##STR3## 
When the degree of polymerization of the organosiloxane exceeds 10,000, the 
resultant composition becomes so viscous that its bleedout on the surface 
prior to curing does not proceed smoothly. On the other hand, if the 
degree of polymerization is less than 2, the bleedout after curing takes 
place excessively. Accordingly, the degree of polymerization is in the 
range of from 2 to 10,000, preferably from 3 to 5,000. 
If the amount of the fifth ingredient is less than 5 parts by weight per 
100 parts by weight of the first ingredient, a satisfactory releasing 
effect cannot be expected. If the amount is over 60 parts by weight, 
exudation from the putty-like composition is in excess. Thus, the amount 
ranges from 5 to 60 parts by weight. 
The alkyl modification for the fifth ingredient is carried out by addition 
reaction between an organohydrogenpolysiloxane, for example, of the 
following formula 
##STR4## 
and an .alpha.-olefin compound, for example, of the formula, CH.sub.2 
.dbd.CH(CH.sub.2).sub.m' --CH.sub.3, in the presence of platinum or a 
platinum compound under heating conditions to obtain the alkyl-modified 
compound of the formula, 
##STR5## 
The curable organopolysiloxane composition of the invention is readily 
obtained by mixing predetermined amounts of the first to fifth 
ingredients. When stored, it is desirable to provide a two-part system 
including liquid A wherein a platinum-based catalyst is added to the first 
alkenyl group-containing polysiloxane ingredient but the second 
organohydrogenpolysiloxane is not added, and liquid B wherein the second 
organohydrogenpolysiloxane ingredient is added to the first ingredient but 
the third platinum-based catalyst is not added. The fourth and fifth 
ingredients may be added to either liquid A or liquid B, or added to both 
liquids A and B. If necessary, in order to suppress the activity of the 
platinum-based catalyst, various organic nitrogen compounds, organic 
phosphorus compounds and acetylene compounds may be added to the 
composition. In addition, pigments, dyes and/or perfumes may be added, if 
desired. 
Since the composition of the invention comprises the alkyl-modified 
siloxane as the fifth ingredient, the liquids A and B can be readily mixed 
or kneaded when used. After curing, the alkyl-modified siloxane does not 
exude as readily as liquid paraffin, enabling one to make a precise 
impression and to make it easy to color the impressed surface. 
Accordingly, the composition of the invention is useful as an impression 
for the human body such as an impression of the teeth or hand, and is 
especially useful when cured articles after completion of impressions are 
long preserved. Moreover, the composition may have wide utility as 
impressions for a vertical face or bodies and for identification and 
electric insulation. 
The present invention is described in more detail by way of examples. 
Synthetic and comparative examples are also described. 
SYNTHETIC EXAMPLE 
100 g of an SiH group-containing siloxane of the formula, 
##STR6## 
and 1 g of an alcohol solution of chloroplatinic acid having a Pt content 
of 2 wt % were placed in a 500 ml three-necked flask equipped with a 
condenser and heated to 80.degree. C. While agitating with a magnetic 
stirrer, 200 g of CH.sub.2 .dbd.CH(CH.sub.2).sub.5 CH.sub.3 was dropped 
through a dropping funnel in about two hours. Thereafter, the mixture was 
heated to 100.degree. C., followed by agitation for further two hours to 
complete the reaction. At this time, it was confirmed that no SiH group 
was left. The resultant reaction product was cooled down to room 
temperature, into which 1.5 g of activated carbon was charged and mixed at 
room temperature for 2 hours, followed by filtration to remove the 
platinum. The reaction product was heated under reduced pressure at 
200.degree. C./5 mmHg for 3 hours to remove unreacted CH.sub.2 
.dbd.CH(CH.sub.2).sub.5 CH.sub.3 therefrom, thereby obtaining a long-chain 
alkyl-modified compound of the following average composition 
##STR7## 
The product had a viscosity of 100 centistokes and a refractive index of 
1.45. 
EXAMPLE 1 
80 parts by weight of a dimethylpolysiloxane oil blocked with a 
dimethylvinylsiloxy group at both ends of the molecular chain and having a 
viscosity of 2,500 centistokes (hereinafter referred to simply as 
vinylsiloxane oil), 20 parts by weight of a dimethylpolysiloxane raw 
rubber having a viscosity of 1,000,000 poises, blocked with a 
dimethylvinylsiloxy group at both ends of the molecular chain and having a 
content of the vinyl group of 0.012 mole % (hereinafter referred to simply 
as siloxane raw rubber), 0.3 parts by weight of an octyl alcohol-modified 
solution of chloroplatinic acid (having a Pt content of 1 wt % and 
hereinafter referred to simply as platinum catalyst), 180 parts by weight 
of quartz powder having an average size of 4 .mu.m, and 30 parts by weight 
of an alkyl-modified siloxane oil of the following average formula 
obtained in the Synthetic Example (hereinafter referred to simply as 
modified siloxane oil) 
##STR8## 
were uniformly mixed by the use of an agitator to obtain putty A. 
On the other hand, 75 parts by weight of the vinyl siloxane oil, 20 parts 
by weight of the siloxane raw rubber, 5 parts by weight of 
methylhydrogenpolysiloxane blocked with a dimethylhydrogensiloxy group at 
both ends of the molecular chain and having 17 mole % of 
methylhydrogensiloxane units (hereinafter referred to simply as H 
siloxane), 180 parts by weight of the quartz powder, 20 parts by weight of 
diatomaceous earth and 30 parts by weight of the modified siloxane oil 
were similarly mixed by means of an agitator to obtain putty B. 
Putties A and B were provided in equal amounts and mixed by hands, followed 
by curing at 60.degree. C. for 1 hour. The cured product was allowed to 
stand for 1 month but no exudation of the modified siloxane oil was 
observed. 
COMATIVE EXAMPLE 1 
In the same manner as in Example 1, 80 parts by weight of the vinyl 
siloxane oil, 20 parts by weight of the siloxane raw rubber, 0.3 parts by 
weight of the platinum catalyst, 180 parts by weight of the quartz powder, 
20 parts by weight of diatomaceous earth, and 30 parts by weight of liquid 
paraffin were uniformly mixed by the use of an agitator to obtain putty 
A-1. 
On the other hand, 75 parts of the vinyl siloxane oil, 20 parts by weight 
of the siloxane raw rubber, 5 parts by weight of the H siloxane, 180 parts 
by weight of the quartz powder, 20 parts by weight of diatomaceous earth 
and 30 parts by weight of liquid paraffin were similarly mixed by means of 
an agitator to obtain putty B-1. 
The putties A-1 and B-1 were provided in equal amounts and mixed by hands, 
followed by curing at 60.degree. C. for 1 hour. The cured product was 
allowed to stand for 3 days but excessive exudation of the liquid paraffin 
was observed. 
EXAMPLES 2 TO 5 AND COMATIVE EXAMPLE 2 
The general procedure of Example 1 was repeated except that the modified 
siloxane oil was replaced by the following four modified siloxane oils 
(Examples 2 to 5) obtained in the same manner as in Synthetic Example and 
a methylphenylsiloxane oil of the formula indicated below (Comparative 
Example 2) and each composition was cured at 60.degree. C. for 1 hour and 
that in Example 5, the H-siloxane compounded in the putty B was used in an 
amount of 15 parts by weight. 
##STR9## 
The respective cured products were each allowed to stand at room 
temperature for 1 month. As a result, it was found that the products of 
Examples 2 to 5 involved no exudation of the oil. With the composition of 
Comparative Example 2, the mixture became a sticky paste, not giving a 
putty.