DE10012817A1 - New hydroxyalkyl cellulose lactate esters useful for making biodegradable thermoplastic resins and fiber-reinforced composite materials - Google Patents

Abstract

Hydroxyalkyl cellulose lactate esters (I) are new. Cellulose ether esters of formula (I) are new: Cell = a cellulose unit with 3 OH groups in the cellulose chain; n = 400-8000; A = H or (CO-CHR1-O)mX; m = (a) 1-40, provided that the average degree of substitution (DS) for CO-CHR1-O is more than 6, or (b) 1-6, provided that the average degree of substitution (DS) for CO-CHR1-O is; B = an ether group comprising 1-5 ethylene oxide, butylene oxide or propylene oxide units, provided that the DS for B is 1 or less; R1 = 1-2C alkyl; X = H or acetyl, provided that the DS for acetyl is 3 or less. An Independent claim is also included for a process for producing (I).

Description

The present invention relates to biodegradable cellulose ether esters have low water absorption, their production and their use for Manufacture of thermoplastic materials or fiber composite materials with natural fibers.

Such materials made from natural raw materials must also have one high technical requirements regarding strength, water resistance and Mechanics are sufficient, but on the other hand they should also be completely biological Degradability under composting conditions within a rot cycle of 3 Months as a prerequisite for disposal via composting lichen.

Cellulose-2-hydroxycarboxylic acid esters have already been reported in the literature. In DE 33 22 118 describes cellulose esters which are produced by reacting Cellulose with dilactide or glycolide in cellulose-specific solvent systems how to make dimethylacetamide / LICl. According to this method, only succeeds Lich the synthesis of low-substituted, water-soluble cellulose derivatives, which as Coating agents or consistency regulators can be used. Because of Their water solubility and lack of thermoplasticity are such cellulose esters for the production of materials due to unsatisfactory properties not suitable. WW 5490 also describes water-soluble and solvent soluble cellulose ether esters.

DE 43 17 231 describes the production of cellulose ester mixed graft polymers saten from moist alkali cellulose in a one-pot reaction by successive addition of alkene oxides and lactones. This allows water-insoluble pro Manufacture products with thermoplastic properties, but form under them  Reaction conditions always large amounts of by-product. In case of A by-product reaction with lactone mainly produces a homopolymer sat of the lactone.

The rate of biodegradation of conventional cellulose derivatives is depending on the level of substitution of each saccharide unit (J.G. Batalaan, The Handbook of Environmental Chemisry, Vol. 3, Part F, Ed. Huntinger, Springer Verlag, 1992, 229-336; M. G. Wirick, Journal of Polymer Science, Part A-1, 6 (1968), 1705-1718). So all technically available cellulose derivatives are only included average degrees of substitution less than 1.0 biologically sufficiently fast degradable. In contrast, thermoplasticity is known in known derivatives such. B. Cellulose Acetate can only be achieved with degrees of substitution greater than 2.5 (T. Eicher, Ullmann's Encyclopedia of Technical Chemistry, 4th Edition, Volume 9, 1975, 227 to 246).

The object of the present invention is accordingly to provide water-insoluble Licher and thermoplastically processable cellulose derivatives, which are used as materials such. B. for the production of foils, fibers or other commodities depending on Need can be used, absorb little or no water and under Composting conditions are as completely biodegradable as possible.

According to the invention, this is achieved by reacting cellulose ether esters with medium degrees of substitution MS _E <1 with the cyclic dimers of 2-hydroxycarboxylic acids to cellulose ether esters with MS _lactate <6, which may also contain acetyl groups in addition to 2-hydroxycarboxylic acid groups, the end-OH groups the 2-hydroxycarboxylic acid or oligo-2-hydroxycarboxylic acid are optionally esterified by acetic acid.

MS _E is defined as the average degree of substitution of the basic cellulose unit in the reaction with alkene oxides over all three free OH groups.

MS _lactate is defined as the average degree of substitution of the basic cellulose ether unit in the reaction with dilactide.

It must be regarded as extraordinarily surprising that it is possible to build up highly substituted cellulose ether esters (MS _E <1, MS _lactate <6) that are completely biodegradable, where the person skilled in the art knew that only cellulose derivatives with average degrees of substitution MS _E less than 1 , 0 are rapidly biodegradable.

The cellulose ether esters according to the invention can be described by the general formula (1):

in which
Cell represents a cellulose unit with 3 OH groups in the cellulose chain, and
n is a value between 400 and 8000,
A is hydrogen or the group - (CO-CR ₁ HO) _m -X where
m is values between 1 to 40, and
B means an ether group formed from ethylene oxide, butylene oxide or propylene oxide having 1 to 5 repeating units
R _{1 is} C ₁ to C ₂ alkyl or hydrogen and
X is hydrogen or a residue

means, the substitution pattern of the mean degrees of substitution MS _E ≦ 1, MS _lactate <6, preferably 6 to 30, particularly preferably 10 to 25 and optionally MS _acetate ≦ 3.

In a variant of the invention, the substitution pattern of the mean degrees of substitution can also be MS _E ≦ 1, MS _lactate = 1-6 and then the end OH groups must be acetylated MS _acetate ≦ 3.

MS _acetate is defined as the average degree of substitution of the end OH groups in the reaction with acetic anhydride to form end acetic acid esters. MS _{lactate + acetate} = total MS _latex + MS _acetate .

B represents an ether group formed from ethylene oxide, butylene oxide or preferably propylene oxide, which may also be oligomeric with 1 to 5 repeating units, but the MS _E with a group B at least 0.4 to 1.5, but preferably 0.4 to 0 , Is 95.

The radical A is preferably lactate acid, dimilctic acid or oligo lactic acid, unsubstituted for X = H, or with a corresponding carboxylic acid, preferably substituted acetic acid.

In an alternative embodiment, one or both of groups A which are bonded directly to the OH group of the cellulose unit can form mixed esters

be substituted with R = C ₁ to C ₂ alkyl.

For the synthesis of the cellulose ether esters according to the invention, the cellulose ether is in suspended in an organic solvent and either purely thermally Cooking uncatalyzed or implemented in the presence of a catalyst, one the cyclic dimer of 2-hydroxycarboxylic acid under anhydrous conditions admits and 1 to 250 hours as required, but preferably 2 to 50 hours Reaction temperatures between 50 and 150 ° C, preferably between 80 and 130 ° C. stirs. The mixed substitution takes place in the same way, with the difference that in addition to the cyclic dimer of 2-hydroxycarboxylic acid at the end of the Main reaction a monocarboxylic anhydride is added and for reaction brought.

Special solvents such as DMAc / LiCl are not required for this.

The anhydrous state of the starting reaction mixture is preferred by Azeotropic drying is achieved, with that in the solvent and the reagents containing residues of water are removed.

Suitable cellulose ethers are, for example, alkyl and aryl celluloses such as. B. hydroxybutyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, particularly preferably hydroxypropyl cellulose and their mixed ethers. The degrees of substitution MS _E are <or = 1, but particularly preferably from 0.4 to 0.95.

Glycolide are particularly suitable as cyclic dimers of 2-hydroxycarboxylic acids, Dilactide and the cyclic dimers of 2-hydroxy-n-butyric acid and 2-hydroxy isobutyric acid, the pure isomers or the isomer mixtures can be used. The dilactide is preferred, namely in high-purity LL Dilactid form, consisting of ~ 90% LL-Dilactid and ~ 10% DL-Dilactid, making about 95% L-lactic acid can be installed.  

For post-substitution in order to produce mixed cellulose ether esters, monocarboxylic acid anhydrides such as C ₂ - to C ₄ -carboxylic acid anhydrides, for. B. acetic, propionic and butyric anhydride.

Suitable suspending agents or solvents are ketones, ethers and cyclic ones Ethers, acetals, anisole, hydrocarbons such as xylene and toluene and aprotic Compounds such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, Dioxane, tetrahydrofuran, N-methylmorpholine, N-methylmorpholine oxide, N-methyl pyrrolidone, dimethoxymethane, dimethyl ether and diethylene glycol dimethyl ether.

If appropriate, the reaction can also be carried out without a solvent when all the raw materials are used in a very dry state.

The reaction can be carried out under basic, coordinative or acid catalysis. It can also be activated with ultrasound or with microwave radiation.

Amines such as triethylamine and 1,8-diazabi can optionally be used as catalysts cyclo [5.4.0] undecen-7 or basic anhydrous metal salts such as sodium acetate, Sodium carbonate, potassium acetate, potassium carbonate and lithium carbonate used become. In addition, tin and zinc salts, as are more common, are also suitable be used for the synthesis of polylactide, if by appropriate Measures to ensure that oligomerization or polymerization of the dimeric 2-hydroxycarboxylic acid occurs.

By varying the underlying cellulose ether and the ester groups as well The choice of suitable degrees of substitution can be thermoplastic and under com Posting conditions biodegradable cellulose ether esters with melting points obtained between 100 and 190 ° C, which with the conventional processing tech Technics for thermoplastics such as extrusion, injection molding or blow molding can be processed are. Another variant is the cellulose ether esters according to the invention  for the production of blends with other esters such as polylactic acids, polyhydroxy Mix butyric acids or polyamide esters.

The cellulose ether esters according to the invention are particularly notable for Stiffness, strength as well as transparency and gloss. Regarding their material properties are similar to conventional, non-compostable polystyrene.

The cellulose ether esters according to the invention with MS _lactate ≦ 10 are generally amorphous substances, as can be demonstrated by X-ray measurements. They still have a significant water absorption capacity, which reduces the strength properties.

A particularly advantageous form of the hydroxyalkyl cellulose ether esters according to the invention with only low water absorption are therefore those in which MS _lactate ≧ 18. In these, all 3 groups A in formula (1) are substituted with radicals of the formula - (CO-CR ₁ HO) _m -X (where X = H), in which m is at least 6. This is due to the fact that, with the right choice of solvent and the appropriate reaction temperature, these A groups are arranged in a helical manner and the OH at the lactate chain end saturates through intramolecular hydrogen bonding and the cellulose ether ester can thus crystallize, thereby minimizing water absorption. The crystallization could be verified by X-ray measurement. However, crystallization is only possible if the synthesis temperature is around 100 ° C. and toluene, xylene or dioxane are preferably used as solvents. If, on the other hand, the synthesis is carried out in xylene at about 140 ° C, the product is amorphous, which can easily be demonstrated by the X-ray measurement - due to the missing X-ray signal.

Dissolve or suspend this amorphous product z. B. in toluene and leaves at about 100 ° C evaporate the solvent again, so shows the dried product X-ray signal again. This means that the crystalline order can be obtained at around 100 ° C also produce afterwards.  

Another possibility of achieving a very low water absorption even in the case of compounds according to the invention with low MS _lactate is to not allow any free OH groups, ie X = H, in group A in formula (1), but rather to react all groups X with carboxylic acid groups . This means that even with a MS _lactate = 3, sufficiently low water intakes can be achieved.

With the cellulose ether esters according to the invention, highly substituted, manufacture thermoplastically processable and compostable compounds that excellent material properties, especially high rigidity exhibit.

Further objects of the invention are the use of the cellulose ether esters thermoplastic materials or for the production of fiber composite materials.

The cellulose ether esters according to the invention are suitable for the production of Molded parts such as bottles, flower pots, dishes, foils for packaging for Food and organic waste, mulch films, baby diapers, etc. They are still for the production of coatings for flat packs such as paper, tiles, Fabrics or other substrates or for the production of fiber blends and Laminates and fiber composite materials are suitable. This invention Materials are suitable in addition to the production of biodegradable work substances for the production of bottles, fibers, foils and other shaped bodies for the production of blends of any composition with other biological degradable components such. B. starch, cellulose, polylactide, polyglycolide, poly hydroxybutyric acid, polycaprolactone, polyester amides, copolyesters or poly ester urethanes. The modification with aids such. B. plasticizers, anti oxidants, weather stabilizers, flame retardants, dyes, shock toughness modifiers such as natural rubber and pigments are possible. Farther succeeds in producing compostable anisotropic fiber composites by introducing natural fibers such as flax, ramie, sisal or hemp.  

The cellulose ether esters according to the invention can also be used as matrix material Formulation of active ingredients e.g. B. for pheromones, fertilizers, fungicides, insecticides, Herbicides or nematocides can be used.  

Examples

All cellulose ether esters made according to the following examples are organic degradable and compostable according to DIN V 54 900.

example 1

26.75 g of hydroxypropyl cellulose (MS _E 0.89) were added to 1250 ml of dioxane. The mixture was heated to boiling and dioxane was distilled off until the boiling point had reached 100 ° C. Then 324 g LL-dilactide was added. The mixture was briefly distilled again and then stirred at 100 ° C. for 212 hours until, after the GC analysis, practically no more LL-dilactide could be detected in the solvent. It was evaporated in a water jet vacuum. 330 g of product were obtained. After crushing, the mixture was stirred in methyl tert-butyl ether, crushed, suction filtered and dried in vacuo. 271 g of hydroxypropyl cellulose lactate with a softening point of 85 to 120 ° C. were obtained. The MS _lactate value was 16.7. According to the GPC examination, 30.59% with an M _W <10000 were present (measured in dichloromethane).

Example 2

26.7 g of hydroxypropyl cellulose (MS _E 0.89) were introduced into 1000 ml of toluene. The mixture was heated to boiling and about 50 ml of toluene were distilled off with a little water. 144 g of LL-dilactide were then added. The mixture was briefly distilled again and then stirred at 100 ° C. until, after a GC-dilactide residue determination in the solvent, practically no more LL-dilactide could be detected. After about 25 hours, the mixture was evaporated in vacuo, the residue was stirred with methyl tert-butyl ether, ground, suction filtered and dried in vacuo. 137 g of hydroxypropyl cellulose lactate with a softening point of 90 to 110 ° C. were obtained. The MS _lactate value was 11.0.

Example 3

26.7 g of hydroxypropyl cellulose (MS _E 0.89) were introduced into 1000 ml of toluene. It was heated to boiling and about 100 ml of toluene was distilled off with a small amount of water. Then 360 g of LL-dilactide were added, about 80 ml of toluene were distilled off again and the mixture was then stirred at 100 ° C. until, after the GC-dilactide residue determination, practically no more LL-dilactide could be detected. After about 25 hours, the mixture was evaporated, the residue was stirred with methyl tert-butyl ether, crushed, filtered off and dried in vacuo. 340 g of hydroxypropyl cellulose lactate with a softening point of 80 to 105 ° C. were obtained. The MS _lactate value was 29.

Example 4

26.7 g of hydroxypropyl cellulose (MS _E 0.89) were stirred in 1300 ml of xylene at 100 ° C. for 30 minutes. 210 ml of xylene were then distilled off with a little water, 180 g of LL-dilactide were added, another 140 ml of xylene were distilled off and the mixture was stirred with boiling for 6 hours until, after the GC-dilactide residue determination in the solvent, practically no more LL-dilactide could be detected. The xylene was then decanted (90 ml) and the remaining mixture was evaporated in vacuo. The residue was stirred in methyl tert-butyl ether, crushed, filtered off and dried in vacuo. 184 g of hydroxypropyl cellulose lactate were obtained. The MS _lactate value was 17.0. This sample initially had no X-ray signal. The usual X-ray signal only appeared again after dissolving in toluene and again evaporating at 100 ° C.

Example 5

26.6 g of hydroxypropyl cellulose (MS _E 0.89) were boiled in 1250 ml of toluene. 240 ml of toluene were then distilled off with a little water. Subsequently, 180 g of LL-dilactide were added, another 180 ml of toluene were distilled off and the mixture was then stirred at 110 ° C. for 25 hours until practically no more LL-dilactide could be detected in the solvent by GC-dilactide determination. Then 41 g of acetic anhydride were added dropwise at 100 ° C. and stirring was continued for 20 hours. The supernatant solvent was decanted off and the gelatinous residue was evaporated in vacuo. 210 g of hydroxypropyl cellulose lactate acetate were obtained. The MS _{lactate + acetate} value was 22.6. A value of 6.5% for M _W <10,000 was determined by GPC.

Example 6

214 g of hydroxypropyl cellulose (MS _E 0.89) were heated to boiling in 2000 ml of toluene. Then 555 ml of toluene was distilled off with a little water. 237 g of LL dilactide with 500 ml of fresh toluene were then added, and 330 ml of toluene were distilled off again. After stirring for 15 hours, almost no LL-dilactide could be detected by GC-dilactide residue determination. It was suctioned off and dried in vacuo. 423 g of hydroxypropyl cellulose _lactate with an MS _lactate value of 2.9 were obtained.

212 g of this hydroxypropyl cellulose lactate were then boiled in 2000 ml of toluene. Then 300 ml of toluene were distilled off and 500 ml of acetic anhydride were added. The mixture was stirred at 100 ° C. for 2 days, then evaporated in vacuo, dried and ground. 251.5 g of hydroxypropyl cellulose _{lactate acetate} with an MS _{lactate + acetate} value of 5.3 were obtained. 11.87% for M _W <10000 were determined by GPC.

Example 7

214 g of hydroxypropyl cellulose (MS _E 0.89) were heated to boiling in 2000 ml of toluene. Then 550 ml of toluene were distilled off. 79 g of LL-dilactide with a further 500 ml of toluene were added, and 330 ml of toluene were still distilled off while boiling. Then the mixture was stirred at 110 ° C. for 15 hours, filtered off and dried in vacuo. 269 g of hydroxypropyl cellulose _lactate with an MS _lactate value of 1.1 were obtained.

134.5 g of this hydroxypropyl cellulose lactate were heated to boiling in 2000 ml of toluene. 300 ml of toluene were then removed by distillation. Then 500 ml of acetic anhydride were added and the mixture was stirred at 100 ° C. for 2 days. It was evaporated in vacuo, dried and crushed. 158 g of hydroxypropyl cellulose _{lactate acetate} with an MS _{lactate + acetate} value of 3.3 were obtained. 13.5% for M _W <10000 were determined by GPC.

Other cellulose ether esters were prepared analogously.

Using examples 1 to 3, table 1 shows the water absorption during water storage, measured in each case on 2 samples per example. The LL-dilactide ratio was chosen higher and higher per mole of hydroxypropyl cellulose. In Table 1 it is now shown that the water absorption decreases with increasing MS _lactate value. At the same time, it is indicated whether there is crystallinity after the X-ray measurement.

Table 1

Based on the behavior of Examples 5 to 7 in water storage, Table 2 shows that even with low MS _lactate, low water uptake can be achieved by substituting the free OH groups with acetate (water storage 2 samples per example).

Table 2

The value of the water absorption of polyamide 6 is also given for comparison.

Polymer-physical data are summarized in Table 3:  

Table 3

The degrees of substitution can be analyzed using the usual methods of cellulose derivatives such as. B. Zeisel splitting, elemental analysis, gas chromatography and ¹³ C-NMR spectroscopy. The softening points were determined on a Kofler bank.

Claims (8)

1. Cellulose ether esters of the general formula
in which
Cell a cellulose unit with 3 OH groups in each cell chain,
n is a value between 400 and 8000,
A is hydrogen or the group - (CO-CR ₁ HO) _m -X, where
m is a value between 1 to 40, and
B represents an ether group formed from ethylene oxide, butylene oxide or propylene oxide having 1 to 5 repeating units, and
R _{1 is} C ₁ or C ₂ alkyl and
X is hydrogen or a residue
means, the substitution pattern of the mean degrees of substitution MS _E ≦ 1, MS _lactate <6 and optionally MS _acetate ≦ 3. 2. Cellulose ether according to claim 1, characterized in that MS _{lactate represents} a value between 6 and 30. 3. Cellulose ether esters of the general formula
in which
Cell a cellulose unit with 3 OH groups in each cell chain,
n is a value between 400 and 8000,
A is hydrogen or the group - (CO-CR ₁ HO) _m -X, where
m is a value between 1 to 6, and
B represents an ether group formed from ethylene oxide, butylene oxide or propylene oxide having 1 to 5 repeating units, and
R _{1 is} C ₁ or C ₂ alkyl and
X is hydrogen or a residue
means, where the substitution pattern or mean degrees of substitution MS _E ≦ 1, MS _lactate <1-6 and optionally MS _acetate ≦ 3. 4. A process for the preparation of cellulose ether esters of the formula (1), characterized in that

• a) suspended a cellulose ether in an organic solvent and
• b) if appropriate in the presence of a catalyst and anhydrous conditions, with the cyclic dimer of a 2-hydroxycarboxylic acid for 1 to 250 hours at reaction temperatures between 50 and 150 ° C. with stirring,
• c) optionally adding acetic anhydride and
• d) the reaction product is isolated from the solvent in a conventional manner and dried.

5. The method according to claim 4, characterized in that in Ver Step (b) as a cyclic dimer of a 2-hydroxycarboxylic acid dilactide is used. 6. The method according to claims 4 to 5, characterized in that as Cellulose ether in process step (a) hydroxyethyl cellulose, hydroxy propyl cellulose or hydroxybutyl cellulose is used. 7. Use of a hydroxyalkyl cellulose ether ester of the formula (1) for Manufacture of thermoplastics. 8. Use of a hydroxyalkyl cellulose ether ester of the formula (1) for Manufacture of fiber composite materials.