WO2001018093A1

WO2001018093A1 - Method for obtaining polyamidoamine-epichlorhydrin resin suited for making wet-strength paper with low monochloro-3-propanediol-1,2 content

Info

Publication number: WO2001018093A1
Application number: PCT/FR2000/002386
Authority: WO
Inventors: Gérard Constantin; Stéphane Fouquay; Chantal Poulet; Isabelle Silberzan
Original assignee: Ceca S.A.
Priority date: 1999-09-03
Filing date: 2000-08-28
Publication date: 2001-03-15
Also published as: AU7017500A; FR2798132A1; EP1254189A1; FR2798132B1

Abstract

The invention concerns a method for obtaining polyamidoamine-epichlorhydrin resins (PAE) suited for making wet-strength paper with low monochloro-3-propanediol-1,2 content. The method consists in synthesizing resins as such, which are then percolated on activated carbon columns. Thus aqueous resins are obtained free of detectable organo-chlorinated by-products, which are used as wet-strength additives for making paper for special uses containing less than 50 ppb of monochloro-3-propanediol-1,2.

Description

PROCESS FOR OBTAINING POLYAMIDOAMINE RESIN

EPICHLORHYDRIN SPECIFIC TO THE MANUFACTURE OF RESISTANT PAPERS

LOW MOISTURE IN MONOCHLORO-3-PROPANEDIOL-1.2.

The present invention relates to additives of the polyamidoamine-epichlorohydrin type used to impart wet strength to special papers for medical, cosmetic or food use (tea bag, coffee filter, etc.), with the aim of limiting the retention of AOX, (put for "adsorbable organically halo-people") in particular dichloro-1, 3-propanol-2 and especially 3-monochloro-1, 2-propanediol (MCPD) in papers incorporating such resins.

Polyamidoamine-epichlorohydrin type resins are low molecular weight polymers which can be crosslinked at neutral pH. They are produced industrially in two stages: a polycondensation reaction at high temperature (around 160 ° C) between adipic acid and diethylene triamine followed by an alkylation-quaternization with epichlorohydrin. Sometimes, and this is the case of the resins of the invention, they are purified by passing over a bed of adsorbent, in this case active charcoals.

The general structure of these resins has been shown in FIG. 1. It is the azetidinium structure which is said to provide the wet strength to the treated paper.

For the sake of clarity, the following abbreviations will be used below, which are moreover common for those skilled in the art:

- PA to denote the polycondensate between adipic acid and diethylene triamine, - PAE to denote the polyamidoamine-epichlorohydrin resin,

- PAEe to specify the PAE resin before percolation (resin at the column entry),

- PAEp to designate the PAE resin after percolation (resin at the column outlet), - DETA to designate diethylene triamine,

- PPE to designate epichlorohydrin,

- MCPD to designate monochloropropanediol (monochloro-3-propane-diol-1, 2),

- DCP to designate dichloropropanol (dichloro-1, 3-propanol-2). MCPD and DCP are by-products of the preparation of PAE. They have been recognized, especially MCPD, toxic and mutagenic. Their elimination is the aim of the process according to the invention. The different reactions present during the synthesis of a PAE resin have been summarized in FIG. 1 Epichlorohydrin reacts on the secondary amino functions, as well as on the primary amino functions of PAE, by forming HCl chlorohydroxypropane groups, there azetidinium groups by intramolecular cyclization of the preceding The resulting PAE resin is an oligomeric molecule having a random distribution of azetidinium groups, organo-chlorinated side groups and residual secondary amino functions The alkylation reaction of PA by epichlorohydrin is unfortunately not total, and a few hundred ppm of epichlorhydnne hydrolyze into organo-chlorinated by-products, mainly DCP and MCPD

In order to solve this problem, producers have long been concerned with supplying PAE resins with a low level of DCP and MCPD, sometimes at the cost of a significant loss of efficiency. so-called foodstuffs which are required to have a high resistance in the wet state, in particular papers for the production of coffee filters or tea bags or herbal teas, the MCPD specifications in the paper are extremely low, less than 100 ppb or even 50 ppb, and very difficult to respect even with commercial PAE resins containing less than 1 ppm of MCPD

The problem of preparing PAE resins suitable for such uses (used at high dosages, between 7 and 8% of commercial PAE on dry fibers) is all the more difficult as the link between the MCPD content of the PAE resin and the MCPD content in the treated paper is very loose It is indeed found that with various commercial PAE resins at 11 - 14% dryness, the MCPD level of which is the same level, ie between <1 and 20 ppm, resins that l '' can be obtained for example by purification by percolation on a bed of ion-exchange resin (WO 92/22601 - AKZO NV) or of activated carbon (WO 93/21384 - DU PONT DE NEUMOURS and FR 2,736,644 - CECA SA), obtains papers which, although produced under the same conditions, some measure some 50 ppb of MCPD, others more than 300 ppb And we can also see that a commercial PAE of 1 1 to 14% of dry titrating 200 ppm of MCPD, as well as that which results from its purification to less than 1 ppm of MCPD p both led to papers with high titer in residual MCPD

The Applicant proposes as a solution to this hitherto unsolved problem, a very efficient and very economical process, object of the present invention, for producing, after selective trapping on active carbon of AOX, PAE resins containing less than 1400 ppm of total AOX, less than 10 ppm of DCP and PPE and of <10 to 180 ppm of MCPD - these values being corrected for dryness of the percolated PAE resin - and more particularly making it possible to obtain papers wet resistants themselves containing less than 100 ppb of residual MCPD, or even less than 50 ppb.

This is achieved by preparing the PAEp resin according to the invention as follows: (1) condensing adipic acid and DETA, the adipic acid / molar ratio

DETA being chosen between 0.98 and 1.02, in order to obtain an intermediate polyamidoamine (PA) at 60.0 ± 0.5% in aqueous solution of total alkalinity of between 3.0 and 3.4 meq / g , preferably between 3, 1 and 3.3 meq / g, and of viscosity less than 2000 mPa.s. measured at 23 ° C. (2) reacting the polyamidoamine with epichlorohydrin (PPE) in the aqueous phase - the quantity of epichlorohydrin being calculated according to the total alkalinity of the base PA, ie 0.36 to 0.91 mole of epichlorohydrin by eq / g of total basic alkalinity (or respectively 0.40 to 1.00 mole per mole of DETA contained in the base), and preferably 0.45 to 0.86 (or respectively 0.50 to 0 , 95 mole per mole of DETA contained in the base) - in order to obtain an aqueous solution of viscosity at 20 ° C between 20 and 300 mPa.s after adjusting the dryness between 13 and 25%, preferably between 14 and 20 % sec. (3) adjust the pH to 20 ° C between 2.3 and 4.0 with sulfuric acid. (4) percolate the PAEe resin as obtained in (3) on an activated carbon column, stopping the percolation when the total MDCP content of the percolated PAEp resin, expressed relative to the dry resin, does not exceed 180 ppm, preferably 90 ppm and preferably 10 ppm. The DCP and PPE contents of these resins do not exceed 10 ppm expressed in the same way. These values are very easily obtained by working with weight ratios of percolated resin, expressed by weight of dry resin, on weight of carbon of between 1.0 and 1.4 depending on the dryness of the resin. The usual analytical characteristics of an EAP according to the invention as obtained at the end of step (3), corrected for dryness are grouped in table A below:

* Experimental values determined at Mutek @ (particle charge detector)

The usual analytical characteristics of a PAEp according to the invention as obtained at the end of step (4), corrected for dryness are grouped in table B below.

Experimental values determined with Mutek® (particle charge detector) The coals useful for the invention are very generally those which are recommended for discoloration and purification of aqueous solutions, with an iodine index (according to ASTM D 4607-86 standard) of at least 500 mg / g, preferably greater than 900 mg / g The activated carbon which has loaded with AOX can be regenerated at high temperature (around 900 ° C) with a "make up", adding a certain proportion of new activated carbon in regenerated carbon from 5 to 10% in new activated carbon While certain processes only concentrate the organo-chlorines in the adsorbent and the problem remains of their elimination, activated carbon, because it regenerates at high temperature, allows their transformation into water, CO2 and HCI which can be eliminated without danger

The unexpected consequence is that not only PAEp resins _. resulting from the process according to the invention do not lose their capacity to impart wet strength to the paper - there is a 10 to 40% gain in wet strength compared to the PAEe - but that they make it possible to obtain papers containing less 50 ppb of MCPD for utilization rates of less than 1% expressed as dry PAE compared to dry fibers These resins according to the invention are particularly appreciated for making paper for medical, cosmetic or food contact use, such as coffee or tea bags

EXAMPLES

In the examples which follow, the DCP, the MCPD and the PPE are assayed by gas chromatographic analysis on a SUPERWAX polyethylene glycol phase column with flame ionization detection. The assay of the MCPD in the paper is carried out according to the following protocol (analysis current circular for Standardization purposes)

- hot aqueous extraction of the MCPD contained in the paper,

- adsorption of MCPD extracted on mineral phase (Extrelut®),

- extraction of MCPD with ethyl ether, - chemical denatilization of MCPD,

- assay by GC / MS analysis

The test papers are prepared from a fibrous suspension made up of 80% long unbleached natural fibers refined at 60 ° Shopper-Riegler (standard NF Q 50-003) and 20% short fibers refined at 25 ° Shopper-Riegler, at a grammage of 15 g / m ² PAE is used at a rate of 7% of commercial product relative to the weight of dry fibers The crosslinking time of PAE is 10 minutes, leaves baked at 105 ° C To determine the resistance of the paper, two strips (test pieces) of paper 180 mm long and 15 mm wide are cut from each form. The first is used to determine the resistance length on wet paper, the second to determining the resistance length of dry paper The tests used are tensile strength tests, carried out in accordance with standard NF Q 03-004 The tensile tests are carried out with an ADAMEL Lhomargy device, set to a speed of 50 mm / min The force F expressed in Newtons which it was necessary to apply to break the strip makes it possible to evaluate the breaking strength R (RH or RS, depending on whether it is a wet break or a break at sec) by the breaking length L, calculated in meters from the expression

LR (m) = 1 / 9.81 F width ^{1 basis} weight ^-1 in which the width is taken in meters and the basis weight in kilograms per square meter The displayed measurements of the LRs by which the REH value is calculated are means of five tests tensile tests performed on five test pieces, each from these five separate formulas

The tensile tests on a dry paper strip are carried out after a minimum of 24 hours of conditioning at 23 ° C and 50% humidity The tensile tests on the wet paper strip are carried out according to standard NF Q 03-056 on strips which , unless otherwise indicated, have been immersed for 1 hour in tap water at a constant temperature of 25 ° C, wrung out and then tested according to a rigorous procedure described in the standard. The wet strength REH is taken as the ratio of the breaking length wet to dry break length expressed in percent

Example 1 Synthesis of a ¹ e PAE according to the invention

In a high temperature reactor of 300 liters of the GRIGNARD type equipped with a thermocouple and a condenser are successively added 16 kg of softened water, 72 kg of DETA and 102 kg of adipic acid (stoichiometry DETA / adipic acid = 1 ) The reaction medium is brought gradually between 155 and 160 ° C. and then maintained at this temperature for 12 hours in order to distill the process and reaction water formed during this polycondensation reaction. Then 99 kg of softened water are gradually added in order to '' obtain 234 kg of an aqueous polyamidoamine (PA) solution with a dry extract of 60%, a viscosity of 1000 to 2000 mPa s (23 ° C) and an alkalinity of 3.2 0.1 meq / g

After transferring these 234 kg into a 2 m ³ stainless steel reactor, this aqueous polyamidoamine solution is cooled to 25 ° C. and then 57 kg of epichlorohydrin (PPE / DETA stoichiometry = 0.90) are added in 1 hour between 25 and 35 ° C maximum, then the reaction medium is kept stirring between 30 and 35 ° C for 2 hours then diluted with 520 kg of permuted water

The resulting solution is brought to 60 ° C and maintained at this temperature until the Zahn viscosity (1 G cup) reaches 42 - 43 seconds at 55 ° C at this time, 370 kg of deionized water are added very quickly and the pH of the solution adjusted to 3 with a 58% sulfuric acid solution

The characteristics of EAP ¹ e in solution are grouped in Table C below

^* Experimental values determined with Mutek®

Example 2 Synthesis of a PAE ^ JD according to the invention

1700 liters of PAE ¹ e resin described in Example 1 are percolated through an adsorber containing 150 kg of a column of activated carbon, in an iodine index granule 1000 mg / g (GAC® 1240), previously saturated with water at the rate of 250 to 300 liters / hour The characteristics of the percolated resin PAE ^ ρ _. in solution are grouped in table D below

Experimental values determined with Mutek®

Example 3 Synthesis of a PAE ^ e not in Accordance with the Invention The 234 kg of intermediate polyamidoamine (PA) are prepared as described in Example 1

After transferring these 234 kg into a 2 m ³ stainless steel reactor, this aqueous polyamidoamine solution is cooled to 25 ° C. and then 69 kg of epichlorohydrin

(PPE / DETA stoichiometry = 1.09) are added in 1 hour between 25 and 35 ° C maximum, then the reaction medium is kept stirring between 30 and 35 ° C for 2 hours then diluted with 520 kg of water Rotated

The resulting solution is brought to 60 ° C and maintained at this temperature until the Zahn viscosity (1 G cup) reaches 42 - 43 seconds at 55 ° C at this time, 673 kg of deionized water are added very quickly and the pH of the solution adjusted to 3 with a 58% sulfuric acid solution

The characteristics of the ³ rd EAP in solution are grouped in Table E below

^* Experimental values determined with Mutek®

Example 4 Synthesis of a PAE ^ g not in accordance with the invention 1700 liters of PAE resin ³ e are percolated as described in Example 2 The characteristics of the percolated resin PAE ^ p _. in solution are grouped in the following table F

Experimental values determined with Mutek®

Example 5 (Synthesis of a PAE -5 e, according to the invention EPI / DETA rate of 0 7) The 234 kg of intermediate polyamidoamine (PA) is prepared as described in Example 1 After transferring these 234 kg into a 2 m3 stainless steel reactor, this aqueous polyamidoamine solution is cooled to 25 ° C. and then 43 5 kg of epichlorohydrin (stoichiometry EPI / DETA = 0 7) are added in 1 hour between 25 and 35 ° C maximum, then the reaction medium is kept stirring between 30 and 35 ° C for 2 hours then diluted with 520 kg of deionized water The resulting solution is brought to 60 ° C and maintained at this temperature until the Zahn viscosity (1 G cup) reaches 42-43 seconds at 55 ° C at this time 530 kg of deionized water are added very quickly and the pH of the solution adjusted to 3 with a 58% sulfuric acid solution

The characteristics of the ⁵ th EAP are grouped in Table G below

TABLE G

* experimental values determined with Mutek ¹ ®

Example 6 Synthesis of a PA p ⁶ according to the invention

Is percolated 1700 liters of resin PAE ^5th described in Example 5 through an adsorber containing 150 kg of an activated carbon column, iodine index granule 1,000 mg / g (GAC ^® 1240), previously saturated with water at a rate of 250 to 300 liters / hour The characteristics of the percolated resin PAE ⁶ p in solution are grouped in Table H below TABLE H:

Example 7 (comparative) - WER evaluation on tea bag type paper The example here is that of an industrial test which illustrates the impact of the resins according to the invention on the level of residual MCPD present in the paper. The resins used are those of examples 2 and 6 in comparison with an industrial quality resin of the PAE ⁴ p type prepared according to the counterexample 4. The following results are obtained:

Claims

1. Process for obtaining polyamidoamine-epichlorohydrin resins with very low PPE contents, 3-monochloro-1, 2-propanedιol, dιchloro-1, 3-propanol-2 and epichlorohydrme suitable for the manufacture of papers with wet resistance and themselves low in 3-monochloro-1, 2-propanedιol, characterized in that i) condensing adipic acid and DETA between 155 and 160 ° C, the molar ratio adipic acid / DETA being chosen between 0 , 98 and 1.02, and the reaction product is dissolved in water in order to obtain a dry extract of between 59.5 and 60.5%, n) the polyamidoamine thus obtained is reacted with epichlorohydrin to aqueous phase, the amount of epichlorohydrin being from 0.40 to 1.00 mole per mole of DETA used in i), m) the pH is adjusted to 20 ° C between 2.3 and 4.0 to the sulfuπque acid, - iv) the aqueous resin is percolated as obtained in (m) between

13 and 25% dry, and preferably between 14 and 20% dry, on an activated carbon column by stopping percolation when the total content of 3-monochloro-1,2-propanediol of the percolated resin, expressed relative with dry resin, does not exceed 180 ppm, preferably 90 ppm and preferably 10 ppm

2. Method according to claim 1, in which the quantity of preferred epichlorohydrin used is from 0.50 to 0.95 mole per mole of DETA

3. Method according to claims 1 or 2, wherein the activated carbon is an activated carbon whose iodine index is greater than 500 mg / g, and preferably greater than 900 mg / g

4. paper treatment composition, consisting of a resin as obtained according to the method of claims 1 to 3, in aqueous solution whose dry extract is between 10.0 and 20.0%, and preferably between 11 , 0 and 15.0%

5. Application of the compositions according to claim 4 to the manufacture of papers for coffee filters and tea bags or herbal teas

6. Application of the compositions according to claim 4 to the manufacture of papers for medical, cosmetic or food contact use, or of papers for industrial use requiring high purity such as filters