CA2169448A1 - Dithio-containing anti-yellowing agents for pulp and paper - Google Patents
Dithio-containing anti-yellowing agents for pulp and paperInfo
- Publication number
- CA2169448A1 CA2169448A1 CA 2169448 CA2169448A CA2169448A1 CA 2169448 A1 CA2169448 A1 CA 2169448A1 CA 2169448 CA2169448 CA 2169448 CA 2169448 A CA2169448 A CA 2169448A CA 2169448 A1 CA2169448 A1 CA 2169448A1
- Authority
- CA
- Canada
- Prior art keywords
- polymer
- thiol
- pulp
- molecular weight
- polyethylene glycol
- 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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
- D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
- D21H21/143—Agents preventing ageing of paper, e.g. radiation absorbing substances
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
- C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
- C08G65/32—Polymers modified by chemical after-treatment
- C08G65/329—Polymers modified by chemical after-treatment with organic compounds
- C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
- C08G65/332—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof
- C08G65/3324—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof cyclic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
- C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
- C08G65/32—Polymers modified by chemical after-treatment
- C08G65/329—Polymers modified by chemical after-treatment with organic compounds
- C08G65/334—Polymers modified by chemical after-treatment with organic compounds containing sulfur
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
- C08L71/02—Polyalkylene oxides
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/1026—Other features in bleaching processes
- D21C9/1047—Conserving the bleached pulp
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Novel substantially odour-free polymeric thiol-containing antioxidant compounds suitable for preventing light induced brightness reversion or yellowing of pulps and papers are described. The novel compounds are based on a polymeric backbone having thiolactate or thioglycolate groups grafted onto the ends thereof and are soluble in water or alcohol.
Description
:=
Dithio-cont~inin~ Anti-Yellowing Agents for Pulp and Paper B~ .ound of Invention This apr~ n is a co~ tion in part of our prior app~iC~tin U.S. serial nllmher 08/261~275~ ~cscll~ly pen~in~, Field of Imention This invention relates to the processes and compounds as anti-yellowing agents or ~(ltli~ionc for pulp and paper. More particularly this invention relates to thio-ester compounds for increasing and st~bili7in~ brightnecc in chemim~ch~nical pulps and papers.
Bach~l.,u.ld of Invention It is well k~own that several org~noslllfilr compounds are effective agents for increasing and st~hili7ing brightnec~c in ch~-m;merh~niç~l pulps and papers. Indeed a survey of the effects of molecular structure of a variety of S CQ~ g compounds on their efflc;~rie,c in such ble~rhin~ and bri~htn~cc st~bili7~tion has been condllcted by Cole and ~S~rk~nton rrappi 72, 117 (1987); they con~hlde(l that uplilllu~ll results were effecteA by certain monomçric thiols such as 1-thioglycerol and glycol dimercapto~cet~te, and that tli.clllfid~.s, snlfoYi~es, slllfn~-,c and most thioethers were relatively ineffective agents in colll~alisolL
It has been clem~m.ctrated that many of the re~ctions involved in the photoyellowing processes in chemim~rh~nic~l and therm~mech~nic~l pulps and - -~ ~ ~ 2 1 69448 ... .. ~
WO 9~/35331 PCT/CA95/00349 _ papers are free radical in nature, and in particular result from photochemical reactionc of lignin macromolecules to generate free radicals. It has also been lçTnr)nstrated that oxy and peroxy radicals are particularly d~m~in~ interrnerli~te~
in photoyellowing processes; it is ~re~u~ed that the erlh~nced ble~çllin~ and protection against reversion afforded by thiols results from their well documlonte~
free radical s~ve~ g and facile hydrogen rlon~ting ~hilih~s. However, mnnomeric thiols such as those described by Cole and Sarkanen are expensive and possess prohibitively noxious odours. In a~flition, once the thiol group has reacted the agent is no longer an active ~tioxi~l~nt; thus relatively high charges (--5-75~o) must be used.
In previous ESR studies both in colution with model lignin chromophores and in bleached and unbleached papers the relatively high effectiveness of thiolactic acid in lJrevelllion of brightnecs reversion has been observed. The synergistic e~ects of compounds such as ascorbic acid in prolonging the effectiveness of thiols as antinYitl~ntc by repair of the initially oYitli7e~ SH group are well known and similar to the synergistic effects of ascorbic acid and phenolic ~nti~ a~ntc such as Vitarnin E.
Without wishing to be bound by this hypothesis, it is believed that the presence of an ~-carbonyl fimction, such as that found in thiol~ctic or thioglycolic acid may proYide a route for repair of the thiol fi-nrtion in an analogous f~chion prolonging the effective lifetime of the ~ntioYid~nt and ~I~;n;~;,;ng the necesc~ry r quantity added.
- ~ 21 6q448 In order to mitig~te the odour problem associated with thiol~ctic or thioglycolic acid and other thiols it is now proposed by the present invention to graft th~ te or thioglycolic groups onto the ends of a polymeric backbone so as to produce a compound which is o~ollrlecc, Lr~spareflt and soluble in water, alcohols, ~etcne and tolllçn.o.
O~iect of Invention Thus it is an object of the present invention to provide novel polymeric thio-ester compounds which are useful to p~;vt;~l photo-yellowing of pulp and paper, which are soluble in selecte~l solvents and which are relatively odour-free.
Brief Statement of Invention Thus, by one aspect of this invention there is provided a substantially odour-free di-thiol graft to a water soluble polymer which comprises a polymeric backbone having thio-ester end groups grafted at the two t~rmin~l groups thereof.
By another aspect of this invention there is provided a process for st~bili~ing brightnPsc of chemime~h~nical pulp and paper co...~ ;..g treating said pulp and paper with an effective ~m~nnt--of a subst~nti~lly odour-free water soluble dithol polymer.
Brief Description of Drawingc Figure 1 is a graph illu~ Lillg the effect of selected polyethylene glycol ithiol~ct~te on photoindllce~l brightn~cc loss in bleached TMP paper;
2 1 69448 ~
Figure 2 is a graph illustrating the effect of the polyethylene glycol thiol~ct~tes of Figure 1 on photoindnce~ brightnecc loss in bleached pulp.
Figure 3 is a graph, similar to Figure 1, illustrating the effect of ~ririitir)n~l selectedpolyethyleneglycol-thiol~rt~tesorthioglycolatesonphoto-inducedbrightnr.cc loss in ble~-he~ TMP paper; and Figure 4 is a graph of th~rrn~l gravimetric aIlalysis of PEGS~
Detailed Description of Plcfelled Embodiments Suitable grafting substrates for use in the present invention are polyalkylene water soluble polymers which have thio-ester end groups grafted at the two te~ al groups thereo This process is also known as "end-capping". Polyalkyle~es such as polyethylene, poly~ropylene and ll~Lures thereof are especially prefell ed. C'çllnlocic polymers may also be employed but polyamides are not particularly snit~le~
Preferably the molecular weight of the end-capped polyallylene glycol is in the range 200~000, and most preferably in the range 600-1700.
Thiol sllbstih-ent.c include those from thiolactic acid and thioglycolic acid.
Other polymeric backbones have also been utili7efl~ in~lutling polyvinyl alcohoIs (degree of suhstitl-tion varying from 15% - 85%. MW 10,000.-20,000), and polymeric carbohydrate backbones inrl~ltling (but not limited to) soluble starch and r~tionic starch (co~ telL~ily amine groups). The thiol modified polyvinyl alcohols showed no efficacy in brightnecs reversion inhibition at lo~-lin~s of 5-7%. The addition of thiol snhstit~lte~l starches to the pulp samples increased the initial , - -_ WO 95/35331 briEhtn~-cs values as compared to the pulps/papers with a corresponding lo~Aing of the ~ms~bstih~ted starch but did not appear to decreace the rate of brightnecs loss u~der subsequent irr~di~tion at the lo~din~c used (5-10%).
ID order to illu~llale the present inventio~ more srerifi~ ~lly thiol sllhstitllte-l polyethylene glycol polymers with molecular weights v~yillg between 600 and 3400 were synthçci7erl While most of the work rc~olLed herein has been done with thi~ Ct~te SllhstiblteA PEG, it is to be noted that at the 2000 MW range, the thioglycolate snkstitllteA PEG gave çcce~ti~11y iclentir~l results. Ihese polymers were ~lPciEn~tetl as PGI12600, PGII~ 800, PG11~1100 and PGI121700, having molecular weights of 600, 800, 1100 and 1700 respectively. PGI12600 and PGI~2800 are viscous liquids while PG1~1100 and PGI121700 are solids at room temperature.
All polymers are soluble in ~lcohQl and all but PGI~2600 are water soln~le. ~11 are çccçnti~lly o~lonrl~cc, Synthesis of the polymers was effected by con-~encing 30g of the polyethylene glycol with 2.5 equivalents of thiol~rtic acid in tohlene (40 ml) under acidic conditi~nc at 85-90C for 12 hours.- At two hour intenals some water and tolllen~
were removed under reduced ples~ule; ~d-lition~l toluene was then added to the initial reaction volume. The yields of polyethylene glycol ~lithin~ t~t~s were between about 83% a~d 90%.
~ ~- -; 2 1 69448 ~
F,Y~mple 1 Tre~tm~nt of TMP paper (Black Spruce) with polyethylene glycol ~lithi~ ct~tec, .S~mrles of ble~rhed TMP paper (P~pric~n, Montreal) were treated with meth~nt~l sollltinnc co..~ g 3% PG~L2600, 3.2% PGllz800, 43% PGI12-1100 and 6.7% PGI~L21700 (all in wt%) respectively, so that the -SH group con~ c ..I ~Lion in each test sohltion was the same (ie 0.062 mol/L). The samples were then dried, covered with a pyrex~ plate and irr~r1i~ted with a 200 W super I les~ule mercury lamp posi~ione~l 80cm away for celçctetl standardized periods of time up to about 6 hours. Diffuse Pcefl~ct~nre observations were made at 457 nm using a Labsphere RSA-HP-84 ~ecec~oly coupled to an Oriel ~llticpec spectrometer. Control tests were also perforTned using meth~nnl alone, and glycol lithio~cetate. (NOTE the paper refers to thiol~ctic acid as well but Figure 1 does not show this). The results are shown graphically in Figure 1.
FY~mrl~ 2 Tre~tm~-nt of ble~rhe~l pulp with polyethylerle glycol llithiol~rt~tes S~mrles of ble~che~ pulps (Millar Western Pulp (Meadow Lake) Ltd.) were treated with aliquots of the test mrth~noic sollltion~ as cle~ be~ in FY~mple 1. The pulp s~mrles were dried, exposed to uv light, and di~use reflect~n~e obselv~Lions were made as in F~y~rnrle 1. The results are illustrated graphically in Figure 2.
` ~ 17 ` ~; 2 1 6 9 4 4 ~ PCTICA9510034~
As can be seen from Figures 1 and 2 the results with pulp are very similar to those achieved with paper. Over a period of 4 hours of irr~di~tioll the PGTL~-1700 polymer lost only 13 points in bri~htn~C-C and PGI12-400 lost 23 and 4.6 points respectively. In co~ sl papers treated with glycol dimerc~to~cet~te lost 8.7 and the ullL[eated control lost 15.2. While the reason for the diLre~ lces in ~ l,lion of bri~htn~o.ss reversion with polymer chain length is uncertain, it is believed that water solubility and chain length compatibility with pore size may be res~o~.ible.
Synthesis of PEG-SH
One equivalent of PEG was cQn~lence~ with 2.5 equivalents of thiol (thiol~ctic acid) in a ~.. ;... n ~mount of tohlçn~ necessary for li.csolutir~n A catalytic amount of c~ entrated sulphuric acid was added (0.05 rnL) and the solution heated (80-90C) with stirring for 12 h. The solvent was removed under vacuum, and the residue diluted with diethyl either and stirred until cryst~lli7~tion occurred. The product was filtered, washed with hexane, and dried under vacuum. Yields were typically in excess of 95%. Fc.centi~lly similar results were obtained with thioglycolic acid substihlte-l for this~l~rtic aci;d, and the graph for PEaSH 2~00 ovella~yed therewith.A
Typical lo~-lin~c of 5% by weight of, for eY~mrle, polymer PEG-SH 2000 effect an increase in initial bri~htn~c.c of 4-5 ISO bri~htn~sc points (ISO Bri~htn~occ = Dif~use Reflect~nce measurcd at 457 nm) in ble~rhed C~MP
(chemitherrn(-rnech~nit~l pulp), with a period of subst~nti~l inhibition of yellowing r ~ ", b ' ~ 2 1 6 9 4 4 8 under high int~oncityirr~Ai~tion (A>300 nm) lasting in excess of 4 hr. (These results have been indepen~l~ntly ~ete. ".;..~d to be coll~alable to irr~ tion~ of durations of 36 h or greater with either ultraviolet (Rayonet RPR-100), or intense ~im~ te~
daylight (Xenotest).
These results are shown in Figure 3, where the effects on brightnP.ss reversion inhil~ition, as well as the initial increased briEhtn~-~c for thiol (thiol~ct~te or thioglycolate) sl-hstit-nte~ PEG (PEG-SH 2200) are compared with the untreated pulp (blank), pulp treated with 5% u~nodified PEG 2000, and a typical m-)nomeric thiol EGTBG (ethylene thiol bisthioglycolate 1.5%). Note that for a MW of polymer 2000, the thiol substituted polymer has a MW of 2200 (for thiol~tt~te sllkstitntion) and a 5% load consists of a thiol content of 0.5%.
The pulps used i~ these studies include Hydrogen pero~de ble~ched spruce CI'MP (Blolu~Lol.ville~ Queen's, obtained from Paprican), recycled ~leink~d pulp ~om Fletcher C`.h~lle~ge (Vancouver), Rle~t~hed CI~MP (Elk Falls, B.C, Fletcher Ch~ nge), and ble~ch~ TMP (Millar Western Pulp Ltd., Meadow Lake). In each case the thiol sl~bstit~lte~l polymers gave similar results, i.e. 2-5 points initial bT~ghtn~ss increase, a period of protection of the pulp from yellowing under 4 h high e~ y irr~rli~tion which amounted to an effective 10 point brightn~ss di~elenlial as co"l~aled to unprotected pulps.
Pulp 5~mples were prepared for irr~di~tion by first drying and slightlygrintlin~
the chosen pulp. The desired lo~ling of polymer is added in aqueous solution, therl the pulp sample is pressed into thick sheet. The sheets were then placed 80 crn in front of a super ~i~s~uic 200 W mercury larnp filtered to remove wavelen~thc less than 300 nrn and irr~di~te~l for periods of up to 4 h. The intP-ncity of the lamp was reduced by 30% using layers of metal screening.
Dif~use relect~nce obsenations were made at 457 nm using a r ~bsphere RSA-HP-84 ~ce-ccory coupled to an Oriel Mnlticpec spct;~lullleter.
The principal advantages of the thiol sl-bstitl~ted polymers over monomeric thiol inhihitors include the following:
a the modified polymers are essentially odourless, or possess only a mild odour.
b. except for the polymer made from PEG 400 the products are solids arld are readily water soluble.
c. the polymers are therm~lly stable - therm~l gravimetric analysis of PEG-SH æoo shows no degr~d~tion below 375C (see Figure 4).
Note, that this s~ pstc applic~tinn as a ~oLe~Lial ~ntif~Yifl~nt in Figure 2 many other m~teri~lc int~ in~ polymers.
d. the polymers are also photo~hçmi~lly inert in aqueous solution showing no degr~d~tion after 12-24 h of irr?~ tinn ,, 9 2~ 69448 ~
e. the synthetic route for preparation of the polymers is a simple, one step reaction with facile purifi~tion.
Modifications using other effective thiol, disulphide, or phenolic ~ntic Yi-l~ntc would be sirnple.
f. unlike ~ntioy~ ntc such as ascorbic acid, the PEG-SH polymers have been shown to cause no therm~ ,kel~i"g of pulps and papers. This is very i~nportant since the paper rolls or packages are often stored during shipping etc. for considerable periods before exposure to light during use.
g. spraying of the PEG-SH's onto pulp/papers after they have been irradiated and yellowed returns the pulps/papers to bri~htn~cc values at or closely approaching those prior to irr~ tion VVhile this invention makes particular reference to pulps and paper, the thiol-ester polymers of the invention may also be used to im~ove brightnecc, particularly initial brightnecc of polymeric plastic materials such as poly~midec, polyethylene and poly~llopylene, and in particular nylon.
It will be appreciated by those skilled in the art that the method of irra~ tion with high jntencity uv light to cause accelerated yellowing of the samples is not strictly co-.~ able to yellowing under natural daylight con~itionC. However, these experimt~ntc strongly indicate the dramatic enh~n~ement of protection against reversion afforded by the polyethylene glycol dimercaptol~ct~tec even in col~ , ;con to glycol dimercaptol~t~tP, which with l-thioglycerol, has heretofore provided the 2 ~ 6 ~ 4 4 8 best results. Without wishing to be bound by this explanation, it is believed that the special molec~ r structure of the thiol~ct~tes and thioglycolates both of which have a carbonyl ~ cent to the thiol group is significant~ allowing not only sirnple radical s~avt;~i~g by the thiol forrning a relatively stabie thiol radical, but also subsequently avenues for regeneration of the thiol group prolonging its activity.
Bach~l.,u.ld of Invention It is well k~own that several org~noslllfilr compounds are effective agents for increasing and st~hili7ing brightnec~c in ch~-m;merh~niç~l pulps and papers. Indeed a survey of the effects of molecular structure of a variety of S CQ~ g compounds on their efflc;~rie,c in such ble~rhin~ and bri~htn~cc st~bili7~tion has been condllcted by Cole and ~S~rk~nton rrappi 72, 117 (1987); they con~hlde(l that uplilllu~ll results were effecteA by certain monomçric thiols such as 1-thioglycerol and glycol dimercapto~cet~te, and that tli.clllfid~.s, snlfoYi~es, slllfn~-,c and most thioethers were relatively ineffective agents in colll~alisolL
It has been clem~m.ctrated that many of the re~ctions involved in the photoyellowing processes in chemim~rh~nic~l and therm~mech~nic~l pulps and - -~ ~ ~ 2 1 69448 ... .. ~
WO 9~/35331 PCT/CA95/00349 _ papers are free radical in nature, and in particular result from photochemical reactionc of lignin macromolecules to generate free radicals. It has also been lçTnr)nstrated that oxy and peroxy radicals are particularly d~m~in~ interrnerli~te~
in photoyellowing processes; it is ~re~u~ed that the erlh~nced ble~çllin~ and protection against reversion afforded by thiols results from their well documlonte~
free radical s~ve~ g and facile hydrogen rlon~ting ~hilih~s. However, mnnomeric thiols such as those described by Cole and Sarkanen are expensive and possess prohibitively noxious odours. In a~flition, once the thiol group has reacted the agent is no longer an active ~tioxi~l~nt; thus relatively high charges (--5-75~o) must be used.
In previous ESR studies both in colution with model lignin chromophores and in bleached and unbleached papers the relatively high effectiveness of thiolactic acid in lJrevelllion of brightnecs reversion has been observed. The synergistic e~ects of compounds such as ascorbic acid in prolonging the effectiveness of thiols as antinYitl~ntc by repair of the initially oYitli7e~ SH group are well known and similar to the synergistic effects of ascorbic acid and phenolic ~nti~ a~ntc such as Vitarnin E.
Without wishing to be bound by this hypothesis, it is believed that the presence of an ~-carbonyl fimction, such as that found in thiol~ctic or thioglycolic acid may proYide a route for repair of the thiol fi-nrtion in an analogous f~chion prolonging the effective lifetime of the ~ntioYid~nt and ~I~;n;~;,;ng the necesc~ry r quantity added.
- ~ 21 6q448 In order to mitig~te the odour problem associated with thiol~ctic or thioglycolic acid and other thiols it is now proposed by the present invention to graft th~ te or thioglycolic groups onto the ends of a polymeric backbone so as to produce a compound which is o~ollrlecc, Lr~spareflt and soluble in water, alcohols, ~etcne and tolllçn.o.
O~iect of Invention Thus it is an object of the present invention to provide novel polymeric thio-ester compounds which are useful to p~;vt;~l photo-yellowing of pulp and paper, which are soluble in selecte~l solvents and which are relatively odour-free.
Brief Statement of Invention Thus, by one aspect of this invention there is provided a substantially odour-free di-thiol graft to a water soluble polymer which comprises a polymeric backbone having thio-ester end groups grafted at the two t~rmin~l groups thereof.
By another aspect of this invention there is provided a process for st~bili~ing brightnPsc of chemime~h~nical pulp and paper co...~ ;..g treating said pulp and paper with an effective ~m~nnt--of a subst~nti~lly odour-free water soluble dithol polymer.
Brief Description of Drawingc Figure 1 is a graph illu~ Lillg the effect of selected polyethylene glycol ithiol~ct~te on photoindllce~l brightn~cc loss in bleached TMP paper;
2 1 69448 ~
Figure 2 is a graph illustrating the effect of the polyethylene glycol thiol~ct~tes of Figure 1 on photoindnce~ brightnecc loss in bleached pulp.
Figure 3 is a graph, similar to Figure 1, illustrating the effect of ~ririitir)n~l selectedpolyethyleneglycol-thiol~rt~tesorthioglycolatesonphoto-inducedbrightnr.cc loss in ble~-he~ TMP paper; and Figure 4 is a graph of th~rrn~l gravimetric aIlalysis of PEGS~
Detailed Description of Plcfelled Embodiments Suitable grafting substrates for use in the present invention are polyalkylene water soluble polymers which have thio-ester end groups grafted at the two te~ al groups thereo This process is also known as "end-capping". Polyalkyle~es such as polyethylene, poly~ropylene and ll~Lures thereof are especially prefell ed. C'çllnlocic polymers may also be employed but polyamides are not particularly snit~le~
Preferably the molecular weight of the end-capped polyallylene glycol is in the range 200~000, and most preferably in the range 600-1700.
Thiol sllbstih-ent.c include those from thiolactic acid and thioglycolic acid.
Other polymeric backbones have also been utili7efl~ in~lutling polyvinyl alcohoIs (degree of suhstitl-tion varying from 15% - 85%. MW 10,000.-20,000), and polymeric carbohydrate backbones inrl~ltling (but not limited to) soluble starch and r~tionic starch (co~ telL~ily amine groups). The thiol modified polyvinyl alcohols showed no efficacy in brightnecs reversion inhibition at lo~-lin~s of 5-7%. The addition of thiol snhstit~lte~l starches to the pulp samples increased the initial , - -_ WO 95/35331 briEhtn~-cs values as compared to the pulps/papers with a corresponding lo~Aing of the ~ms~bstih~ted starch but did not appear to decreace the rate of brightnecs loss u~der subsequent irr~di~tion at the lo~din~c used (5-10%).
ID order to illu~llale the present inventio~ more srerifi~ ~lly thiol sllhstitllte-l polyethylene glycol polymers with molecular weights v~yillg between 600 and 3400 were synthçci7erl While most of the work rc~olLed herein has been done with thi~ Ct~te SllhstiblteA PEG, it is to be noted that at the 2000 MW range, the thioglycolate snkstitllteA PEG gave çcce~ti~11y iclentir~l results. Ihese polymers were ~lPciEn~tetl as PGI12600, PGII~ 800, PG11~1100 and PGI121700, having molecular weights of 600, 800, 1100 and 1700 respectively. PGI12600 and PGI~2800 are viscous liquids while PG1~1100 and PGI121700 are solids at room temperature.
All polymers are soluble in ~lcohQl and all but PGI~2600 are water soln~le. ~11 are çccçnti~lly o~lonrl~cc, Synthesis of the polymers was effected by con-~encing 30g of the polyethylene glycol with 2.5 equivalents of thiol~rtic acid in tohlene (40 ml) under acidic conditi~nc at 85-90C for 12 hours.- At two hour intenals some water and tolllen~
were removed under reduced ples~ule; ~d-lition~l toluene was then added to the initial reaction volume. The yields of polyethylene glycol ~lithin~ t~t~s were between about 83% a~d 90%.
~ ~- -; 2 1 69448 ~
F,Y~mple 1 Tre~tm~nt of TMP paper (Black Spruce) with polyethylene glycol ~lithi~ ct~tec, .S~mrles of ble~rhed TMP paper (P~pric~n, Montreal) were treated with meth~nt~l sollltinnc co..~ g 3% PG~L2600, 3.2% PGllz800, 43% PGI12-1100 and 6.7% PGI~L21700 (all in wt%) respectively, so that the -SH group con~ c ..I ~Lion in each test sohltion was the same (ie 0.062 mol/L). The samples were then dried, covered with a pyrex~ plate and irr~r1i~ted with a 200 W super I les~ule mercury lamp posi~ione~l 80cm away for celçctetl standardized periods of time up to about 6 hours. Diffuse Pcefl~ct~nre observations were made at 457 nm using a Labsphere RSA-HP-84 ~ecec~oly coupled to an Oriel ~llticpec spectrometer. Control tests were also perforTned using meth~nnl alone, and glycol lithio~cetate. (NOTE the paper refers to thiol~ctic acid as well but Figure 1 does not show this). The results are shown graphically in Figure 1.
FY~mrl~ 2 Tre~tm~-nt of ble~rhe~l pulp with polyethylerle glycol llithiol~rt~tes S~mrles of ble~che~ pulps (Millar Western Pulp (Meadow Lake) Ltd.) were treated with aliquots of the test mrth~noic sollltion~ as cle~ be~ in FY~mple 1. The pulp s~mrles were dried, exposed to uv light, and di~use reflect~n~e obselv~Lions were made as in F~y~rnrle 1. The results are illustrated graphically in Figure 2.
` ~ 17 ` ~; 2 1 6 9 4 4 ~ PCTICA9510034~
As can be seen from Figures 1 and 2 the results with pulp are very similar to those achieved with paper. Over a period of 4 hours of irr~di~tioll the PGTL~-1700 polymer lost only 13 points in bri~htn~C-C and PGI12-400 lost 23 and 4.6 points respectively. In co~ sl papers treated with glycol dimerc~to~cet~te lost 8.7 and the ullL[eated control lost 15.2. While the reason for the diLre~ lces in ~ l,lion of bri~htn~o.ss reversion with polymer chain length is uncertain, it is believed that water solubility and chain length compatibility with pore size may be res~o~.ible.
Synthesis of PEG-SH
One equivalent of PEG was cQn~lence~ with 2.5 equivalents of thiol (thiol~ctic acid) in a ~.. ;... n ~mount of tohlçn~ necessary for li.csolutir~n A catalytic amount of c~ entrated sulphuric acid was added (0.05 rnL) and the solution heated (80-90C) with stirring for 12 h. The solvent was removed under vacuum, and the residue diluted with diethyl either and stirred until cryst~lli7~tion occurred. The product was filtered, washed with hexane, and dried under vacuum. Yields were typically in excess of 95%. Fc.centi~lly similar results were obtained with thioglycolic acid substihlte-l for this~l~rtic aci;d, and the graph for PEaSH 2~00 ovella~yed therewith.A
Typical lo~-lin~c of 5% by weight of, for eY~mrle, polymer PEG-SH 2000 effect an increase in initial bri~htn~c.c of 4-5 ISO bri~htn~sc points (ISO Bri~htn~occ = Dif~use Reflect~nce measurcd at 457 nm) in ble~rhed C~MP
(chemitherrn(-rnech~nit~l pulp), with a period of subst~nti~l inhibition of yellowing r ~ ", b ' ~ 2 1 6 9 4 4 8 under high int~oncityirr~Ai~tion (A>300 nm) lasting in excess of 4 hr. (These results have been indepen~l~ntly ~ete. ".;..~d to be coll~alable to irr~ tion~ of durations of 36 h or greater with either ultraviolet (Rayonet RPR-100), or intense ~im~ te~
daylight (Xenotest).
These results are shown in Figure 3, where the effects on brightnP.ss reversion inhil~ition, as well as the initial increased briEhtn~-~c for thiol (thiol~ct~te or thioglycolate) sl-hstit-nte~ PEG (PEG-SH 2200) are compared with the untreated pulp (blank), pulp treated with 5% u~nodified PEG 2000, and a typical m-)nomeric thiol EGTBG (ethylene thiol bisthioglycolate 1.5%). Note that for a MW of polymer 2000, the thiol substituted polymer has a MW of 2200 (for thiol~tt~te sllkstitntion) and a 5% load consists of a thiol content of 0.5%.
The pulps used i~ these studies include Hydrogen pero~de ble~ched spruce CI'MP (Blolu~Lol.ville~ Queen's, obtained from Paprican), recycled ~leink~d pulp ~om Fletcher C`.h~lle~ge (Vancouver), Rle~t~hed CI~MP (Elk Falls, B.C, Fletcher Ch~ nge), and ble~ch~ TMP (Millar Western Pulp Ltd., Meadow Lake). In each case the thiol sl~bstit~lte~l polymers gave similar results, i.e. 2-5 points initial bT~ghtn~ss increase, a period of protection of the pulp from yellowing under 4 h high e~ y irr~rli~tion which amounted to an effective 10 point brightn~ss di~elenlial as co"l~aled to unprotected pulps.
Pulp 5~mples were prepared for irr~di~tion by first drying and slightlygrintlin~
the chosen pulp. The desired lo~ling of polymer is added in aqueous solution, therl the pulp sample is pressed into thick sheet. The sheets were then placed 80 crn in front of a super ~i~s~uic 200 W mercury larnp filtered to remove wavelen~thc less than 300 nrn and irr~di~te~l for periods of up to 4 h. The intP-ncity of the lamp was reduced by 30% using layers of metal screening.
Dif~use relect~nce obsenations were made at 457 nm using a r ~bsphere RSA-HP-84 ~ce-ccory coupled to an Oriel Mnlticpec spct;~lullleter.
The principal advantages of the thiol sl-bstitl~ted polymers over monomeric thiol inhihitors include the following:
a the modified polymers are essentially odourless, or possess only a mild odour.
b. except for the polymer made from PEG 400 the products are solids arld are readily water soluble.
c. the polymers are therm~lly stable - therm~l gravimetric analysis of PEG-SH æoo shows no degr~d~tion below 375C (see Figure 4).
Note, that this s~ pstc applic~tinn as a ~oLe~Lial ~ntif~Yifl~nt in Figure 2 many other m~teri~lc int~ in~ polymers.
d. the polymers are also photo~hçmi~lly inert in aqueous solution showing no degr~d~tion after 12-24 h of irr?~ tinn ,, 9 2~ 69448 ~
e. the synthetic route for preparation of the polymers is a simple, one step reaction with facile purifi~tion.
Modifications using other effective thiol, disulphide, or phenolic ~ntic Yi-l~ntc would be sirnple.
f. unlike ~ntioy~ ntc such as ascorbic acid, the PEG-SH polymers have been shown to cause no therm~ ,kel~i"g of pulps and papers. This is very i~nportant since the paper rolls or packages are often stored during shipping etc. for considerable periods before exposure to light during use.
g. spraying of the PEG-SH's onto pulp/papers after they have been irradiated and yellowed returns the pulps/papers to bri~htn~cc values at or closely approaching those prior to irr~ tion VVhile this invention makes particular reference to pulps and paper, the thiol-ester polymers of the invention may also be used to im~ove brightnecc, particularly initial brightnecc of polymeric plastic materials such as poly~midec, polyethylene and poly~llopylene, and in particular nylon.
It will be appreciated by those skilled in the art that the method of irra~ tion with high jntencity uv light to cause accelerated yellowing of the samples is not strictly co-.~ able to yellowing under natural daylight con~itionC. However, these experimt~ntc strongly indicate the dramatic enh~n~ement of protection against reversion afforded by the polyethylene glycol dimercaptol~ct~tec even in col~ , ;con to glycol dimercaptol~t~tP, which with l-thioglycerol, has heretofore provided the 2 ~ 6 ~ 4 4 8 best results. Without wishing to be bound by this explanation, it is believed that the special molec~ r structure of the thiol~ct~tes and thioglycolates both of which have a carbonyl ~ cent to the thiol group is significant~ allowing not only sirnple radical s~avt;~i~g by the thiol forrning a relatively stabie thiol radical, but also subsequently avenues for regeneration of the thiol group prolonging its activity.
Claims (15)
1. A substantially odour-free di-thiol graft to a water soluble polymer which comprises a polymer backbone having thiol-ester ends groups grafted at the two terminal groups thereof.
2. A graft polymer as claimed in claim 1 wherein said water soluble polymer is selected from the group consisting of polyalkylene, carbohydrate and cellulosic polymers.
3. A graft polymer as claimed in claim 2 having a molecular weight in the range 200 - 4000.
4. A graft polymer as claimed in claim 2 wherein said polyalkylene is poly-ethylene-glycol.
5. A graft polymer as claimed in claim 2 having a molecular weight in the range 600-1700.
6. A graft polymer as claimed in claim 3 having a molecular weight in the range 800-1700 and which is water soluble.
7. A liquid graft polymer as claimed in claim 3 having a molecular weight of about 600 and which is soluble in an alcohol.
8. A graft polymer as claimed in claim 1 wherein said thiol-ester groups are selected from the group consisting of thiolactates and thioglycolates.
9. A process for stabilizing and increasing brightness of chemimechanical pulps and papers and polymeric materials comprising treating a selected said pulp, paper, or polymeric material and with an effective amount of a substantially odour-free dithiol graft to a water soluble polymer.
10. A process as claimed in claim 8 wherein said polymer is selected from the group consisting of polyalkylene, carbohydrate and cellulosic polymers.
11. A process as claimed in claim 10 wherein said polyalkylene polymer is a polyethylene glycol dithiolactate, having a molecular weight in the range 600-1700.
12. A process as claimed in claim 11 wherein said polyethylene glycol dithiolactate is added to said pulp or paper in an amount sufficient to provide 0.062 mols/L of -SH groups.
13. A process as claimed in claim 12 wherein said polyethylene glycol dithiolactate is in aqueous solution.
14. A process as claimed in claim 12 wherein said polyethylene glycol dithiolactate is in alcoholic solution.
15. A process as claimed in claim 10 wherein said polyalkylene polymer is a polyethylene glycol dithioglycolate having a molecular weight in the range 600 - 3400.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/261,275 | 1994-06-20 | ||
| US26127594A | 1994-07-25 | 1994-07-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2169448A1 true CA2169448A1 (en) | 1995-12-28 |
Family
ID=22992601
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2169448 Abandoned CA2169448A1 (en) | 1994-06-20 | 1995-06-19 | Dithio-containing anti-yellowing agents for pulp and paper |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2169448A1 (en) |
| WO (1) | WO1995035331A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0734716B1 (en) * | 1995-03-30 | 1999-08-25 | Kao Corporation | Composition for permanent waving of human hair |
| GB9718530D0 (en) * | 1997-09-02 | 1997-11-05 | Clariant Int Ltd | Lining material and method for coating a substrate with such lining material |
| US6527914B1 (en) | 2002-01-30 | 2003-03-04 | Ondeo Nalco Company | Method of enhancing brightness and brightness stability of paper made with mechanical pulp |
| US7341828B2 (en) * | 2002-02-28 | 2008-03-11 | Showa Denko K.K. | Thiol compound, photopolymerization initiator composition and photosensitive composition |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE578775A (en) * | 1958-05-19 | |||
| US2992210A (en) * | 1958-07-09 | 1961-07-11 | Rohm & Haas | Process for the preparation of polymers containing mercapto groupings |
| US3284442A (en) * | 1962-04-03 | 1966-11-08 | Nat Starch Chem Corp | Novel starch ester derivatives |
| US3271387A (en) * | 1962-10-10 | 1966-09-06 | Union Starch & Refining Co Inc | High viscosity starch derivatives |
| US4307225A (en) * | 1978-12-05 | 1981-12-22 | Phillips Petroleum Company | Preparation of alkyl mercaptocarboxylate/dialkyl thiodicarboxylate mixture using sulfur and/or water cocatalyst |
| US4565854A (en) * | 1983-04-07 | 1986-01-21 | Kuraray Co., Ltd. | Polymer having thiol end group |
| US5629047A (en) * | 1990-08-06 | 1997-05-13 | Gencorp Inc. | Method of making functionalized styrene butadiene type latex binders |
-
1995
- 1995-06-19 WO PCT/CA1995/000349 patent/WO1995035331A1/en active Application Filing
- 1995-06-19 CA CA 2169448 patent/CA2169448A1/en not_active Abandoned
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| WO1995035331A1 (en) | 1995-12-28 |
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