CA2007548A1 - Method of producing latex foam material - Google Patents
Method of producing latex foam materialInfo
- Publication number
- CA2007548A1 CA2007548A1 CA002007548A CA2007548A CA2007548A1 CA 2007548 A1 CA2007548 A1 CA 2007548A1 CA 002007548 A CA002007548 A CA 002007548A CA 2007548 A CA2007548 A CA 2007548A CA 2007548 A1 CA2007548 A1 CA 2007548A1
- Authority
- CA
- Canada
- Prior art keywords
- mold
- latex
- foam
- expanded
- foam material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
- B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
- B29C2035/0855—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using microwave
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
- B29C33/06—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means using radiation, e.g. electro-magnetic waves, induction heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2021/00—Use of unspecified rubbers as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/0058—Liquid or visquous
- B29K2105/0064—Latex, emulsion or dispersion
Abstract
ABSTRACT OF THE DISCLOSURE
An expanded latex foam material is produced by charging said expanded latex containing auxiliary agents for gelatinization and vulcanization into a mold comprised of a nonmetallic material, the surface of the mold contacting said expanded latex at the time of charging being at a temperature of 45-100°C, heating the latex in the mold to 100°C within a period of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex, removing the foam material from the mold and washing and drying the foam material obtained.
30/dxk
An expanded latex foam material is produced by charging said expanded latex containing auxiliary agents for gelatinization and vulcanization into a mold comprised of a nonmetallic material, the surface of the mold contacting said expanded latex at the time of charging being at a temperature of 45-100°C, heating the latex in the mold to 100°C within a period of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex, removing the foam material from the mold and washing and drying the foam material obtained.
30/dxk
Description
i4~
l - 23~43-413 BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a method of pro-ducing latex foam material from an expanded latex which contains auxiliary agents for gelatinization, vulcanization, and improvement of processability. The term "latex" is here under-stood to refer to an aqueous suspension of a polymer.
Description of the Background The production and composition of latices suitable for the preparation expanded latex are described in, e.g., German Published Patent Applications No. 37 04 118.5 and 34 47 585Ø
In production of latex foams by the impact foaming method, vulcanizing additives and possibly processing-aid , additives are added to the latex, and the latex is brought to the desired density by the vigorous, forced influx of air.
After the appropriate degree of foaming is achieved, gelatiniz-ing agent is added and the foam is charged to the mold. The mold is closed, and immediately upon or after gelatinization of the foam the mold is inserted into a vulcanization apparatus for vulcanization, which apparatus is normally steam-heated. Following the vulcanization the latex foam mater-ial is removed from the mold as a molded material, and is washed and dried. After removal from the vulcanization apparatus, the molds have a temperature of 95-lOO~C.
After the molded material is removed from the moldl the mold is cooled to below 35C before fresh expanded latex is charged into it. According to German Published Patent Application N. 21 50 872.5, it is possible to charge expanded latex produced according to a specific formula into molds having temperatures of 40-70C.
In the case of large and thick molded pieces, such as are used, e.g. for upholstery and mattresses, it is difficult to produce a foam material of the desired quality with highly uniform structure. With heating from the exterior or by channels present in the mold, the mold is heated first. Heat transfer to the gelatini~ed foam is time-consuming and is relatively nonuniform in the case of thick pieces being molded, because the thermal conductivity of the foam is relatively low. Upon cooling, at least part of the energy employed to heat the metallic mold, which weighs up to several hundred kg is lost, even if the mold is 2~0~
234~3-~13 only cooled to a temperature between 40 and 70C.
~ecause of the long vulcanizatlon time, which may take up to 40 min. for a continuou~ process it is necessary to have a large number of molds, and long heating apparatus, if one wishe~ to produce large molded piece~
without substantial waiting time between successive chargings.
~ lth relatively thlck molded piece~ for instance, Of the order of 10 cm, it i~ unsatisEactory to uYe stéam or hot air for heating. The interior region takes a long time to reach the temperature of the surface. A long vulcanlzation time is required for the interior region to become fully vulcanlzed.
Substantial damage may occur to the foam structure ln the interior region if the temperature rise is too slow; or if gelatinizatlon occur~ at elevated temperature the foam can collapse prior to gelatinization.
Accordlng to U.S. Pat. 2,575,259, the foam can be heated to the desired temperature within 1-3 min if the heat is supplied by a high frequency electric field.
Best results are obtained at a frequency of 6-40 MHz, with optimal re~ults at 15 MHz.
If the temperature riqe is too rapid, the water present in the foam may be vaporized, and the steam may break the pore~ ln the foam, with detrimental :. .: .. .
consequences for the mechanical properties of the foam mate~ial.
The molds used in producing latex foam materials are mostly of the closed type. Only in rare cases are "passing goods" produced in open mold~ or on running belts.
These goods are lnvarlably flat products, and generally their thickness is less than S cm. Thicker molded pieces are preferably produced in closed molds. The mold is nearly always provided with protuberances which extend lnto the mold. These protuberances provide improved heat transer and impede local collapse of the foam and separation of the foam from the cover during the gelatinization phase.
The void spaces formed by the protuberances in the molded pieces facilltate and accelerate drying of the molded pieces. The protuberances may have various shapes. They are nearly always mounted on the inner side of the cover. The cover rest~ on the trough in a manner which is not air-tight. Excess foam, the alr displaced when the mold is charg~d, and the excess pressure produced during the heat-induced gelatinization, escape or are relieved principally through air exit openings present ln the corners of the cover, and between the cover and the trough oE the mold. The excess pressure expels a small part of the foam. This mold flash, which i9 wasted material, must . ~ ' ' ' . : '' : ,: ,, ' ,.' ~ :
~0 7~-ifl~
be removed by hand before recharging the mold. In the case of a density of material of 0.05-0.1 g/cc, a few weight percent oE waste corre~ponds to a large volume by a factor Oe 10-2D. A need therefore continues to exist for an improved method of producing foamed latex products by expansion of a latex in a mold.
SUMMARY OF THE INVENTION
Accordingly, one ob~ect of the present invention is to provide a method of gelatini2ing and expanding a latex material by uniform heating thereby producing a foamed material o~ ùniform pore structure and improved quality.
Another object of the present invention is to provide a method of making a uniformly expanded latex material while mlnlmlzing operational cost~ including apparatus costs.
Still another object of the present invention i~
to provide a method of preparing a uniEormly expanded latex at shortened time~ of gelatinization and vulcanizatlon.
Briefly, these objects and other objects of the present invention a~ hereinafter will become more readily apparent can be attained by a method of producing a latex foamed material from an expanded latex by charging said expanded latex containing ~ 0 tJi7 ~
auxiliary agents for gelatinization and vulcanizatlon into a mold comprised of a nonmetallic material, the qurface oE the mold contacting said expanded latex at the time of charglng being at a temperature of 45-100C, heating the latex in the mold to 100C within a perlod of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex, removing the foam material from the mold and wa~h~ng and drying the Eoam material obtained.
DETAILED DESCRIPTION OF THE PREFJ3RRED EME~ODIMENTS
In the pre~ent invention, the expanded latex i~
charged into a mold compri~ed of a nonmetallic material. The thermal conductivlty of the material i~
< 1 W/m/ K, preferably < 0.3 W/m/ K. Suitable material~ from which the mold i5 made lnclude material~
wherewith in a continuous process the temperature of the interior of the mold is below 100C up to the time of the recharging. Suitable such materials include polysulfone, polycarbonate, polytetraEluoroethylene, polyethylene, and polypropylene. The mold may be constructed of a ~ingle material, or it may be formed from layer~ of different materials. It may be coated or encap~ulated. That i~, it may be comprised of polypropylene or polytetrafluoroethylene on the ln~ide and glass fiber reinEorced plastic on the outside.
.
:
.. .
0 ~3 At the time of charging of the latex foam (expanded latex), the mold may have a temperature Oe 50-100C. In contra~t to customary methoda, the mold doe~ not need to be cooled further, for instance, to temperatures below 35C. It is also unnece~sary to produce the expanded latex according to a ~pecific formula. ~ecause oE the low thermal conductivity o~
the nonmetallic material, no appreciable damage occurs to the latex foam during gelatlnizatlon, even at the locationq at which the foam contacts the walls of the mold. Further, almost all of the heat in the mold as a result of the preceding vulcanization procesq remains in the mold.
For gelatinizatlon and vulcanization, the latex foam, in the mold, is heated to up to 100C by microwaves, in a perlod Oe a few minute~. The microwave~ have a frequency of 1-100 GHz, pre~erably 2-25 GHz. The dimension~ of the microwave field may be adjuqted to those of the mold in known fashion.
The layer thicknesq of the latex foam charged to the mold may be varied over a wide range up to several decimeter~. Even very thick foams are uniformly gelatinized and vulcanized.
The duration Oe exposure oE the latex foam to the microwave Eield depend~ on the power denqity oE the field, the heat required to ~alse the latex foam to the 21t ~ 7 r'2 ~ ~
desired temperature below 10~C and the tlme requir~d to vulcani~e the Eoam. The optlmum duratlon and the power density of the field which ihould be established are determined in a preliminary experiment.
The us~ of microwave field i~ advantageou~ in heating the latex foam to its vulcanization temperature. That temperature obviou~ly depends on the Eormulation, the polymer, and the rate of heating, but not on the type of heating.
At a density of the foam material of 0.1 g/cc, an exposure duration of S min. for a thickness oE 3 cm and 8 min for a thickness of 15 cm can be achieved, lf constant generator power i9 employed.
The present method i8 particularly advantageous when used for continuous molding, but it can also be uaed to advantage with closed molds. The lifter-type protuberances, iE present, are mounted on the interlor side of the bottom of the mold.
Dimens~onal expanslon Oe the foam during thermal gelatinization is taken into account in the height of the mold. ~ccordingly, the descrlbed method doea not produce any mold flash, and there is practically no 1099 of material. This represents a ~ub~tantial economic advantage.
It i8 also possible to carry out gelatinization in a microwave Eield with a conventionally constructed , ,.
~1~3~
' clo~ed mold, as long as the mold is compri~ed o~
nonmetallic materlal.
The method of the pre~ent invention has the Eollowing advantages:
i) The foamed material has a very uni~orm pore structure over its entire volume, and its elongatlon at break behavlor 19 very uniform. ~urther, thiok foam bodies are heated in the microwave Eield from the interior outward, in a uniform fashion, and rapidly.
ii) The foamed material may be produced in greater thickne3ses than foamed material prepared by state of the art methods, and in essentlally flawless quality. For microwave irradiation from one ~ide, foam materials Oe thickness greater than 15 cm and a den3ity of 0.1 g/cc may be produced.
iii) A density of the foamed material of a~ low as 0.04 g/cc may be achleved, with the material still being of e~sentially flawless quality.
iv) More economical formulations may be used for the latex foam. The proportion of processing aids can be reduced, and the proportion of filler~ can be increased, wlthout substantial detriment to the quality of the foamed material.
v) The molds formed oE nonmetallic material loAe practically none of their heat energy between chargings. There! is minimal radlative loss of heat.
Thus, the energy conAumption is low.
,: ' . . : ' .- ,. : ;, ,' ~: :
vl) Only a small number of molds i9 required.
The apparatus for gelatinizing and vulcanizing i~ much smaller than apparatus used with other heat sources.
vii) The molds for heating in the microwave field are free of channel for pas~age of ~team or heating medium, and therefore are unpressurized.
Having now g~nerally described this inventlon, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of lllustration only and are not intended to be limiting unless otherwi~e speciEied.
ExamE~le 1:
A natural latex having a low ammonium content prepared according to a known formula to which auxiliary agent~ had been added, was air-~oamed in known fa~hion, and a gelatinizing agent was added thereto in such a way and in such an amount as estimated to provide a gelatinization time of the latex foam of c. 40 min at about 18C.
A mattress mold was used, having interior dimensions of 200 x 100 x 15 cm. The mold was comprlsed of polypropylene. Its wall thicknes~ was 2 cm, and it was provided with bracing means on its rear side. The mold did not have a cover. Protuberances were mounted on the interior side of the bottom of the mold. The welght of the mold was c. 92 kg.
- . :: . ,, :
t~
The latex foam was charged lnto the open mold and was smoothed by running a doctor blade or the llke over it. The mold had previously been used for gelatinizatlon and vulcanl~ation processes, and at the time oE the charging had a temperature oE 91 C on its interior side. The filled mold was placed in a microwave Eield having a frequency ~.45 GHz. The microwave generator power wa~ c. 24 kW. The specific power was c. 1.2 kW/kg latex Eoam charged, and wa~
approximately uniEormly di~tributed over the surface covered by the foam.
~ ithin 6 min, the temperature at all points of the foam material body had rlsen to slightly below 100C.
The molded foamed body was removed from the mold out~ide of the microwave field, and was washed and drled ln known fashion. The molded body was 13 cm thick and had a density of 0.08 g/cc not taking into account the recesses produced by the abovementioned protuberances.
The still hot mold (89 a on the inside) was immediately charged with an additional batch of latex foam.
For contlnuous manufa~ture of a plurality of molded bodies, lt waR only necessary to have four of the descrlbed molds. At a given time, the fir~t wa3 charged with latex foam, the second was heated in the .
.
.
, . . : ~ .. :. , microwave field, the molded body wa~ removed erom the third, and the fourth was in readinlsss for charging with latex foam.
Example 2:
A styrene-butadiene rubber (SBE~) latex having a butadiene content of 65% was produced analogous to the procedure described in Example 1. Auxiliary agents were added to the latex and the latex was foamed ~P~panded~. The expanded latex was charged into an open mold with inter$or dimen~ions of 200 x 100 x 17 cm without protuberances on the interior sid~ of the bottom~ and was 3moothed by wlping with a doctor blade or the like. ~he charged mold was brought into a microwave field similar to the procedure of Example 1.
Within 6 min, the temperature at all pointa of the foam material body had risen to slightly below 100C, and the foam had been gelatinized and vulcanized.
The molded Eoamed bodies removed from the mold had a density of 0.05 g/cc. They were 14 cm thick with a thicknes3 practically uniform over the entire 2 sq. m surEace. During the gelatinization and vulcanization in the open mold the thickness of the foam was reduced only to the extent of about 18% oÇ the initial thickne3s.
.
..
' : . ~ ~: '' .' ' ' `' "
. ~ :-.-::
~: . - .: .:
~C~0 ~
Havin~ now fully de~cribed the invention, it will be apparent to one of ordinary ~klll in the art that many changes and modiflcationa can be made thereto without departing from the spirit or acope oE the invention as set forth herein.
. . , ~ ~ .
l - 23~43-413 BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a method of pro-ducing latex foam material from an expanded latex which contains auxiliary agents for gelatinization, vulcanization, and improvement of processability. The term "latex" is here under-stood to refer to an aqueous suspension of a polymer.
Description of the Background The production and composition of latices suitable for the preparation expanded latex are described in, e.g., German Published Patent Applications No. 37 04 118.5 and 34 47 585Ø
In production of latex foams by the impact foaming method, vulcanizing additives and possibly processing-aid , additives are added to the latex, and the latex is brought to the desired density by the vigorous, forced influx of air.
After the appropriate degree of foaming is achieved, gelatiniz-ing agent is added and the foam is charged to the mold. The mold is closed, and immediately upon or after gelatinization of the foam the mold is inserted into a vulcanization apparatus for vulcanization, which apparatus is normally steam-heated. Following the vulcanization the latex foam mater-ial is removed from the mold as a molded material, and is washed and dried. After removal from the vulcanization apparatus, the molds have a temperature of 95-lOO~C.
After the molded material is removed from the moldl the mold is cooled to below 35C before fresh expanded latex is charged into it. According to German Published Patent Application N. 21 50 872.5, it is possible to charge expanded latex produced according to a specific formula into molds having temperatures of 40-70C.
In the case of large and thick molded pieces, such as are used, e.g. for upholstery and mattresses, it is difficult to produce a foam material of the desired quality with highly uniform structure. With heating from the exterior or by channels present in the mold, the mold is heated first. Heat transfer to the gelatini~ed foam is time-consuming and is relatively nonuniform in the case of thick pieces being molded, because the thermal conductivity of the foam is relatively low. Upon cooling, at least part of the energy employed to heat the metallic mold, which weighs up to several hundred kg is lost, even if the mold is 2~0~
234~3-~13 only cooled to a temperature between 40 and 70C.
~ecause of the long vulcanizatlon time, which may take up to 40 min. for a continuou~ process it is necessary to have a large number of molds, and long heating apparatus, if one wishe~ to produce large molded piece~
without substantial waiting time between successive chargings.
~ lth relatively thlck molded piece~ for instance, Of the order of 10 cm, it i~ unsatisEactory to uYe stéam or hot air for heating. The interior region takes a long time to reach the temperature of the surface. A long vulcanlzation time is required for the interior region to become fully vulcanlzed.
Substantial damage may occur to the foam structure ln the interior region if the temperature rise is too slow; or if gelatinizatlon occur~ at elevated temperature the foam can collapse prior to gelatinization.
Accordlng to U.S. Pat. 2,575,259, the foam can be heated to the desired temperature within 1-3 min if the heat is supplied by a high frequency electric field.
Best results are obtained at a frequency of 6-40 MHz, with optimal re~ults at 15 MHz.
If the temperature riqe is too rapid, the water present in the foam may be vaporized, and the steam may break the pore~ ln the foam, with detrimental :. .: .. .
consequences for the mechanical properties of the foam mate~ial.
The molds used in producing latex foam materials are mostly of the closed type. Only in rare cases are "passing goods" produced in open mold~ or on running belts.
These goods are lnvarlably flat products, and generally their thickness is less than S cm. Thicker molded pieces are preferably produced in closed molds. The mold is nearly always provided with protuberances which extend lnto the mold. These protuberances provide improved heat transer and impede local collapse of the foam and separation of the foam from the cover during the gelatinization phase.
The void spaces formed by the protuberances in the molded pieces facilltate and accelerate drying of the molded pieces. The protuberances may have various shapes. They are nearly always mounted on the inner side of the cover. The cover rest~ on the trough in a manner which is not air-tight. Excess foam, the alr displaced when the mold is charg~d, and the excess pressure produced during the heat-induced gelatinization, escape or are relieved principally through air exit openings present ln the corners of the cover, and between the cover and the trough oE the mold. The excess pressure expels a small part of the foam. This mold flash, which i9 wasted material, must . ~ ' ' ' . : '' : ,: ,, ' ,.' ~ :
~0 7~-ifl~
be removed by hand before recharging the mold. In the case of a density of material of 0.05-0.1 g/cc, a few weight percent oE waste corre~ponds to a large volume by a factor Oe 10-2D. A need therefore continues to exist for an improved method of producing foamed latex products by expansion of a latex in a mold.
SUMMARY OF THE INVENTION
Accordingly, one ob~ect of the present invention is to provide a method of gelatini2ing and expanding a latex material by uniform heating thereby producing a foamed material o~ ùniform pore structure and improved quality.
Another object of the present invention is to provide a method of making a uniformly expanded latex material while mlnlmlzing operational cost~ including apparatus costs.
Still another object of the present invention i~
to provide a method of preparing a uniEormly expanded latex at shortened time~ of gelatinization and vulcanizatlon.
Briefly, these objects and other objects of the present invention a~ hereinafter will become more readily apparent can be attained by a method of producing a latex foamed material from an expanded latex by charging said expanded latex containing ~ 0 tJi7 ~
auxiliary agents for gelatinization and vulcanizatlon into a mold comprised of a nonmetallic material, the qurface oE the mold contacting said expanded latex at the time of charglng being at a temperature of 45-100C, heating the latex in the mold to 100C within a perlod of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex, removing the foam material from the mold and wa~h~ng and drying the Eoam material obtained.
DETAILED DESCRIPTION OF THE PREFJ3RRED EME~ODIMENTS
In the pre~ent invention, the expanded latex i~
charged into a mold compri~ed of a nonmetallic material. The thermal conductivlty of the material i~
< 1 W/m/ K, preferably < 0.3 W/m/ K. Suitable material~ from which the mold i5 made lnclude material~
wherewith in a continuous process the temperature of the interior of the mold is below 100C up to the time of the recharging. Suitable such materials include polysulfone, polycarbonate, polytetraEluoroethylene, polyethylene, and polypropylene. The mold may be constructed of a ~ingle material, or it may be formed from layer~ of different materials. It may be coated or encap~ulated. That i~, it may be comprised of polypropylene or polytetrafluoroethylene on the ln~ide and glass fiber reinEorced plastic on the outside.
.
:
.. .
0 ~3 At the time of charging of the latex foam (expanded latex), the mold may have a temperature Oe 50-100C. In contra~t to customary methoda, the mold doe~ not need to be cooled further, for instance, to temperatures below 35C. It is also unnece~sary to produce the expanded latex according to a ~pecific formula. ~ecause oE the low thermal conductivity o~
the nonmetallic material, no appreciable damage occurs to the latex foam during gelatlnizatlon, even at the locationq at which the foam contacts the walls of the mold. Further, almost all of the heat in the mold as a result of the preceding vulcanization procesq remains in the mold.
For gelatinizatlon and vulcanization, the latex foam, in the mold, is heated to up to 100C by microwaves, in a perlod Oe a few minute~. The microwave~ have a frequency of 1-100 GHz, pre~erably 2-25 GHz. The dimension~ of the microwave field may be adjuqted to those of the mold in known fashion.
The layer thicknesq of the latex foam charged to the mold may be varied over a wide range up to several decimeter~. Even very thick foams are uniformly gelatinized and vulcanized.
The duration Oe exposure oE the latex foam to the microwave Eield depend~ on the power denqity oE the field, the heat required to ~alse the latex foam to the 21t ~ 7 r'2 ~ ~
desired temperature below 10~C and the tlme requir~d to vulcani~e the Eoam. The optlmum duratlon and the power density of the field which ihould be established are determined in a preliminary experiment.
The us~ of microwave field i~ advantageou~ in heating the latex foam to its vulcanization temperature. That temperature obviou~ly depends on the Eormulation, the polymer, and the rate of heating, but not on the type of heating.
At a density of the foam material of 0.1 g/cc, an exposure duration of S min. for a thickness oE 3 cm and 8 min for a thickness of 15 cm can be achieved, lf constant generator power i9 employed.
The present method i8 particularly advantageous when used for continuous molding, but it can also be uaed to advantage with closed molds. The lifter-type protuberances, iE present, are mounted on the interlor side of the bottom of the mold.
Dimens~onal expanslon Oe the foam during thermal gelatinization is taken into account in the height of the mold. ~ccordingly, the descrlbed method doea not produce any mold flash, and there is practically no 1099 of material. This represents a ~ub~tantial economic advantage.
It i8 also possible to carry out gelatinization in a microwave Eield with a conventionally constructed , ,.
~1~3~
' clo~ed mold, as long as the mold is compri~ed o~
nonmetallic materlal.
The method of the pre~ent invention has the Eollowing advantages:
i) The foamed material has a very uni~orm pore structure over its entire volume, and its elongatlon at break behavlor 19 very uniform. ~urther, thiok foam bodies are heated in the microwave Eield from the interior outward, in a uniform fashion, and rapidly.
ii) The foamed material may be produced in greater thickne3ses than foamed material prepared by state of the art methods, and in essentlally flawless quality. For microwave irradiation from one ~ide, foam materials Oe thickness greater than 15 cm and a den3ity of 0.1 g/cc may be produced.
iii) A density of the foamed material of a~ low as 0.04 g/cc may be achleved, with the material still being of e~sentially flawless quality.
iv) More economical formulations may be used for the latex foam. The proportion of processing aids can be reduced, and the proportion of filler~ can be increased, wlthout substantial detriment to the quality of the foamed material.
v) The molds formed oE nonmetallic material loAe practically none of their heat energy between chargings. There! is minimal radlative loss of heat.
Thus, the energy conAumption is low.
,: ' . . : ' .- ,. : ;, ,' ~: :
vl) Only a small number of molds i9 required.
The apparatus for gelatinizing and vulcanizing i~ much smaller than apparatus used with other heat sources.
vii) The molds for heating in the microwave field are free of channel for pas~age of ~team or heating medium, and therefore are unpressurized.
Having now g~nerally described this inventlon, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of lllustration only and are not intended to be limiting unless otherwi~e speciEied.
ExamE~le 1:
A natural latex having a low ammonium content prepared according to a known formula to which auxiliary agent~ had been added, was air-~oamed in known fa~hion, and a gelatinizing agent was added thereto in such a way and in such an amount as estimated to provide a gelatinization time of the latex foam of c. 40 min at about 18C.
A mattress mold was used, having interior dimensions of 200 x 100 x 15 cm. The mold was comprlsed of polypropylene. Its wall thicknes~ was 2 cm, and it was provided with bracing means on its rear side. The mold did not have a cover. Protuberances were mounted on the interior side of the bottom of the mold. The welght of the mold was c. 92 kg.
- . :: . ,, :
t~
The latex foam was charged lnto the open mold and was smoothed by running a doctor blade or the llke over it. The mold had previously been used for gelatinizatlon and vulcanl~ation processes, and at the time oE the charging had a temperature oE 91 C on its interior side. The filled mold was placed in a microwave Eield having a frequency ~.45 GHz. The microwave generator power wa~ c. 24 kW. The specific power was c. 1.2 kW/kg latex Eoam charged, and wa~
approximately uniEormly di~tributed over the surface covered by the foam.
~ ithin 6 min, the temperature at all points of the foam material body had rlsen to slightly below 100C.
The molded foamed body was removed from the mold out~ide of the microwave field, and was washed and drled ln known fashion. The molded body was 13 cm thick and had a density of 0.08 g/cc not taking into account the recesses produced by the abovementioned protuberances.
The still hot mold (89 a on the inside) was immediately charged with an additional batch of latex foam.
For contlnuous manufa~ture of a plurality of molded bodies, lt waR only necessary to have four of the descrlbed molds. At a given time, the fir~t wa3 charged with latex foam, the second was heated in the .
.
.
, . . : ~ .. :. , microwave field, the molded body wa~ removed erom the third, and the fourth was in readinlsss for charging with latex foam.
Example 2:
A styrene-butadiene rubber (SBE~) latex having a butadiene content of 65% was produced analogous to the procedure described in Example 1. Auxiliary agents were added to the latex and the latex was foamed ~P~panded~. The expanded latex was charged into an open mold with inter$or dimen~ions of 200 x 100 x 17 cm without protuberances on the interior sid~ of the bottom~ and was 3moothed by wlping with a doctor blade or the like. ~he charged mold was brought into a microwave field similar to the procedure of Example 1.
Within 6 min, the temperature at all pointa of the foam material body had risen to slightly below 100C, and the foam had been gelatinized and vulcanized.
The molded Eoamed bodies removed from the mold had a density of 0.05 g/cc. They were 14 cm thick with a thicknes3 practically uniform over the entire 2 sq. m surEace. During the gelatinization and vulcanization in the open mold the thickness of the foam was reduced only to the extent of about 18% oÇ the initial thickne3s.
.
..
' : . ~ ~: '' .' ' ' `' "
. ~ :-.-::
~: . - .: .:
~C~0 ~
Havin~ now fully de~cribed the invention, it will be apparent to one of ordinary ~klll in the art that many changes and modiflcationa can be made thereto without departing from the spirit or acope oE the invention as set forth herein.
. . , ~ ~ .
Claims (8)
1. A method of producing a latex foam material from an expanded latex, which comprises:
charging said expanded latex containing auxiliary agents for gelatinization and vulcanization into a mold comprised of a nonmetallic material, the surface of the mold contacting said expanded latex at the time of charging being at a temperature of 45-100°C;
heating the latex in the mold to 100°C within a period of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex;
removing the foam material from the mold; and washing and drying the foam material obtained.
charging said expanded latex containing auxiliary agents for gelatinization and vulcanization into a mold comprised of a nonmetallic material, the surface of the mold contacting said expanded latex at the time of charging being at a temperature of 45-100°C;
heating the latex in the mold to 100°C within a period of 3-10 minutes at a frequency of 1-100 GHz thereby gelatinizing and vulcanizing said latex;
removing the foam material from the mold; and washing and drying the foam material obtained.
2. The method according to Claim 1, wherein the expanded latex is charged into said mold, the material of which has a thermal conductivity of less than 1 W/m/ K.
3. The method according to Claim 2, wherein the thermal conductivity of the mold material is less than 0.3 W/m/ K.
4. The method according to Claim 1 wherein the microwave field has a frequency of 2-25 GHz.
5. The method according to Claim 1 wherein the expanded latex is charged into an open mold.
6. The method according to Claim 1 wherein the expanded latex is charged into a closed mold which is provided with protuberances on the bottom and on the cover.
7. The method according to Claim 1 wherein the expanded latex is charged into a mold which is comprised of polycarbonate, polysulfone, polytetrafluoroethylene, or polypropylene.
8. The method according to Claim 1 wherein the foamed material has a density as low as about 0.04 g/cc.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3900809A DE3900809A1 (en) | 1989-01-13 | 1989-01-13 | METHOD FOR PRODUCING LATEX FOAM |
| DEP3900809.6 | 1989-01-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2007548A1 true CA2007548A1 (en) | 1990-07-13 |
Family
ID=6371989
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002007548A Abandoned CA2007548A1 (en) | 1989-01-13 | 1990-01-11 | Method of producing latex foam material |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0377808B1 (en) |
| JP (1) | JPH02233233A (en) |
| AT (1) | ATE74062T1 (en) |
| CA (1) | CA2007548A1 (en) |
| DE (2) | DE3900809A1 (en) |
| ES (1) | ES2025048T3 (en) |
| FI (1) | FI900135A (en) |
| GR (1) | GR3004993T3 (en) |
| IL (1) | IL93007A0 (en) |
| NO (1) | NO900210L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2724834A1 (en) | 2012-10-23 | 2014-04-30 | Latexco NV | Method and device for producing a bedding product comprising a foamed latex layer, slab of such foamed latex layer for cutting a bedding product and bedding product obtained |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4207898A1 (en) * | 1992-03-12 | 1993-09-16 | Huels Chemische Werke Ag | MOLD FOR PRODUCING LATEX FOAM |
| DE19503240C2 (en) * | 1995-02-02 | 1997-04-10 | Huels Chemische Werke Ag | Mold for gelation and vulcanization of molded articles made of latex foam using microwave energy |
| US5733944A (en) * | 1995-05-26 | 1998-03-31 | Basf Aktiengesellschaft | Aqueous polymer dispersions |
| DE19541590A1 (en) * | 1995-11-08 | 1997-05-15 | Huels Chemische Werke Ag | Coated mold for the production of molded parts from foamed latex |
| DE10338367B3 (en) * | 2003-08-21 | 2005-04-07 | Dames-Willers Gmbh | Process for vulcanizing latex foam and apparatus therefor |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2428369A1 (en) * | 1978-06-08 | 1980-01-04 | Cim Lambda Int Sarl | Microwave heat treatment - maintaining excess pressure in resonator cavities against workpiece tunnel |
| US4499036A (en) * | 1982-09-20 | 1985-02-12 | W. R. Grace & Co. | Microwave curing of latex-based compositions |
-
1989
- 1989-01-13 DE DE3900809A patent/DE3900809A1/en not_active Withdrawn
- 1989-11-17 AT AT89121271T patent/ATE74062T1/en not_active IP Right Cessation
- 1989-11-17 DE DE8989121271T patent/DE58901043D1/en not_active Expired - Lifetime
- 1989-11-17 ES ES89121271T patent/ES2025048T3/en not_active Expired - Lifetime
- 1989-11-17 EP EP89121271A patent/EP0377808B1/en not_active Expired - Lifetime
-
1990
- 1990-01-08 IL IL93007A patent/IL93007A0/en unknown
- 1990-01-10 FI FI900135A patent/FI900135A/en not_active IP Right Cessation
- 1990-01-11 CA CA002007548A patent/CA2007548A1/en not_active Abandoned
- 1990-01-12 JP JP2003731A patent/JPH02233233A/en active Pending
- 1990-01-15 NO NO90900210A patent/NO900210L/en unknown
-
1992
- 1992-06-19 GR GR920401331T patent/GR3004993T3/el unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2724834A1 (en) | 2012-10-23 | 2014-04-30 | Latexco NV | Method and device for producing a bedding product comprising a foamed latex layer, slab of such foamed latex layer for cutting a bedding product and bedding product obtained |
| WO2014063839A1 (en) | 2012-10-23 | 2014-05-01 | Latexco N.V. | Bedding product comprising a foamed latex layer, slab of such foamed latex layer for cutting a bedding product therefrom and method of manufacturing thereof |
| US10842290B2 (en) | 2012-10-23 | 2020-11-24 | Latexco N.V. | Bedding product comprising a foamed latex layer, slab of such foamed latex layer for cutting a bedding product therefrom and method of manufacturing thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| ES2025048A4 (en) | 1992-03-16 |
| FI900135A (en) | 1990-07-14 |
| FI900135A0 (en) | 1990-01-10 |
| NO900210D0 (en) | 1990-01-15 |
| DE3900809A1 (en) | 1990-07-19 |
| GR3004993T3 (en) | 1993-04-28 |
| ATE74062T1 (en) | 1992-04-15 |
| EP0377808A1 (en) | 1990-07-18 |
| ES2025048T3 (en) | 1994-09-01 |
| DE58901043D1 (en) | 1992-04-30 |
| IL93007A0 (en) | 1990-09-17 |
| EP0377808B1 (en) | 1992-03-25 |
| JPH02233233A (en) | 1990-09-14 |
| NO900210L (en) | 1990-07-16 |
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