Method for manufacturing a fibrous web

Abstract

The invention relates to a method for manufacturing a fibrous web, such as web of paper, board, tissue or the like. The method comprises obtaining at least one fibre suspension of lignocellulosic and / or cellulosic fibres and feeding the fibre suspension into an intermediate residence entity, such as pulper, storage tower or broke tower. Fibre suspension, which comprises bacterial endospores, is discharged out of the intermediate residence entity via an outlet after a residence time of at least 2 hours in the intermediate residence entity and after a time delay the fibre suspension is formed into a fibrous web. Bacterial endospores are sensitised by adding a germinant surfactant, which comprises a primary or secondary ammonium head group and a linear unsubstituted C12-alkyl tail, to the fibre suspension at an addition point, which is located at the lower part of the intermediate residence entity or after the outlet of the intermediate residence entity, but before the formation of the fibrous web.

Description

<DP=1>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²1²METHOD FOR MANUFACTURING A FIBROUS WEB²The present invention relates to a method for manufacture of fibrous web ²according to the preambles of enclosed independent claims.²Bacterial cells are normally present in aqueous environments of pulp mills as ²well ²as paper, board and tissue mills. Bacterial growth in the process is commonly ²monitored and limited by using various measures, e.g. by feeding of biocides ²into ²the process flows. There are also many other ways to destroy or kill ²vegetative²bacterial cells. For example, in manufacture of paper and board the vegetative ²²bacteria are destroyed also by heat in the drying section of a paper or board ²machine. However, some bacterial cells form endospores, which are highly ²resistant to common destruction methods effective for vegetative bacteria, ²such as ²heat, disinfectants, chemical biocides, desiccation, ultraviolet light and ²ionizing²radiation. The endospores may remain viable but dormant for prolonged periods, ²²even for years, until the external conditions become favourable, after which a ²²transformation, i.e. germination, of bacterial endospores into vegetative ²bacteria ²takes place.²The amount of endospores in the final paper or board product may be a problem, ²²especially if the product is intended for hygiene purposes, food packaging or ²beverage packaging. Consequently there is an interest in the paper and board ²production to reduce not only the amount of vegetative bacteria but also the ²dormant endospores.²Problems are often encountered when there is a production stop, either planned ²or ²unplanned, at the paper or board mill. Pulp is stored in large storage towers, ²and ²during the production stop, the conditions in storage towers may change in a ²manner that promotes formation of endospores. During the production stop it is²hard or impossible to feed biocide into the storage tower, at least so that ²the whole ²pulp volume inside the tower could be treated. Furthermore, the large size of ²the ²storage towers may lead to inadequate mixing and / or formation of poorly mixed ²zones inside the tower, even during normal production conditions. After the²<DP=2>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²2²storage tower, especially after a production stop, the pulp may contain too ²much ²endospores, which means that the produced paper or board does not meet the ²quality requirements and must be sold at lower price or completely discarded. ²In ²addition to storage towers, bacterial endospores may cause problems in other²process stages with long residence times, for example in pulpers for pulp and ²broke. Consequently, there is a need for a solution that would enable ²effective ²endospore control immediately after process stages with long residence times, ²especially after pulper(s) and / or the storage tower(s).²There are suggestions to control of spore forming bacteria by nutrient ²triggered ²germination. Germinating agents that function as nutrients, such as L-alanine, ²are ²added to the system and should induce the germination of endospores by ²creating ²a non-hostile environment. The germination requires some delay and the ²germinated endospores would thereafter be destroyed by conventional biocides. ²In²practice, however, addition of germinating agents that function as nutrients ²to a ²process, especially with closed or nearly-closed water circulation, leads ²easily to ²over-nutrification of the whole system, inducing excessive microbial activity ²that ²increases risks for all kind of microbiological issues, such as slime ²formation on ²machinery or formation of malodours. Prevention of these consequences would²require increasing biocide dosages. Nutrient triggered germination has thus ²not ²become a realistic option in industrial systems with closed or nearly-closed ²water ²circulations and / or complex microbial environment.²An object of this invention is to minimise or possibly even eliminate the² disadvantages existing in the prior art.²Another object of the present invention is to provide an effective method for ²quantitatively reducing bacterial endospores in the aqueous environment of ²pulp ²mill, paper mill or board mill, especially after the storage tower or the like ²or after a²production stop.²<DP=3>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²3²A further object of the present invention is to effectively sensitise the ²bacterial ²endospores for obliteration in the aqueous environment of pulp mill, paper ²mill or ²board mill.²These objects are attained with the invention having the characteristics ²presented²below in the characterising parts of the independent claims.²Some preferred embodiments of the invention are presented in the dependent ²claims.² The features recited in the dependent claims and the embodiments in the ²description relate, whenever applicable, both to the method as well as to the ²treatment system, even if not always explicitly stated so.²In a typical method according to the present invention for manufacturing a ²fibrous²web, such as web of paper, board, tissue or the like, the method comprises²(a) obtaining at least one fibre suspension of lignocellulosic and / or ²cellulosic fibres,²(b) feeding the fibre suspension into an intermediate residence entity, such ²as ²pulper, storage tower or broke tower,²(c) discharging fibre suspension, which comprises bacterial endospores, out of ²the²intermediate residence entity via an outlet after a residence time of at least ²2 hours ²in the intermediate residence entity,²(d) forming after a time delay the fibre suspension into the fibrous web,²wherein²bacterial endospores are sensitised for germination by adding a germinant ²surfactant, which comprises a primary or secondary ammonium head group and a ²linear unsubstituted C12-alkyl tail, to the fibre suspension at an addition ²point, ²which is located at the lower part of the intermediate residence entity or ²after the ²outlet of the intermediate residence entity, but before the formation of the ²fibrous²web.²Typical treatment system for sensitising bacterial endospores in a manufacture ²of ²a fibrous web, such as web of paper, board, tissue or the like, comprises²<DP=4>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²4²- a germinant surfactant, which comprises a primary or secondary ammonium ²head group and a linear unsubstituted C12-alkyl tail, and²- at least one biocidal agent.²Now it has been surprisingly found that a germinant surfactant, which ²comprises a²primary or secondary ammonium head group and linear unsubstituted C12-alkyl ²tail, as well as treatment systems comprising such germinant surfactant, ²effectively ²interacts with endospores and sensitises them by disrupting their outer ²protective ²structure in a pulp suspension, even when the germinant surfactant is added²relatively short time before the web formation. It was highly unexpected that ²the²germinant surfactant is able to effectively sensitise endospores in a complex ²environment comprising fibres, optionally organic and inorganic additives, ²such as ²various papermaking chemicals and mineral fillers. The germinant surfactant is ²²able, during short period of time that lapses between the intermediate ²residence²entity and the following process stage, to sensitise endospores in a manner ²that ²transforms them into form in which they can be easily destroyed, either by ²using a ²biocidal agent, heat or by the germinant surfactant itself. The present ²invention ²thus enables manufacture of hygienic paper or board even from an endospore-²containing pulp suspension.² In the present context the term "germinant surfactant" denotes generally a ²compound that comprises a primary or secondary ammonium head group and a ²linear unsubstituted alkyl tail. The germinant surfactant is able to disrupt ²the ²protective outer structure of an endospore and subjects its core to the ²biocidal²agents and / or heat. The germinant surfactant is thus non-nutrient germinant. ²The ²germinant surfactant shows also a biocidal effect itself, i.e. the germinant ²surfactant itself, in suitable concentration, is able to destroy endospores ²and leave ²them unviable. According to one preferable embodiment of the invention the ²germinant surfactant is selected from n-dodecylamine, n-dodecylguanidine,²dodecylamine salt, dodecylguanidine salt or any of their mixtures, more ²preferably²n-dodecylamine or dodecylguanidine salt, such as dodecylguanidine ²hydrochloride ²or dodecylguanidine acetate. Even more preferably the germinant surfactant may ²²be n-dodecylamine or dodecylguanidine hydrochloride.²<DP=5>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²The addition of the germinant surfactant to the fibre suspension of ²lignocellulosic ²and / or cellulosic fibres does not increase the amount of nutrients suitable ²for ²microbial consumption in the suspension. In this way the addition of the ²germinant²5 surfactant does not increase the risk for heightened microbial activity ²in general.²The germinant surfactant may be added, either alone or as a component of the ²treatment system, in amount of > 30 ppm, preferably > 50 ppm, more preferably ²> ²60 ppm, given as active surfactant, to the fibre suspension which contains²bacterial endospores. According to one embodiment the germinant surfactant may²be added in amount that is in the range of 30 ¨ 220 ppm, preferably 60 ¨ 200 ²ppm, ²more preferably 70 ¨ 100 ppm, given as active surfactant, to the fibre ²suspension ²which contains bacterial endospores. The germinant surfactant can be added in ²relatively low dosage levels, which is beneficial for both economic and ²technical² reasons. In this manner, for example, foaming problems and interference with²other paperma king chemicals may be avoided. Furthermore, low dosage level may ²²ensure minute or insignificant amounts of germinant surfactant in the final ²product ²which may be a prerequisite for certain hygienic product grades such as food ²packaging board.²In the present context the term "intermediate residence entity" may be any ²pulp, ²water or broke storage tower or tank or corresponding entity in manufacture of ²²pulp, paper, board, tissue or like, which entity has a residence time of at ²least two ²hours. Preferably the intermediate residence entity is pulp tower, water tank, ²broke²storage tower or pulper. In one embodiment of the invention the intermediate ²residence entity is a pulper for pulp or broke. At least one fibre suspension ²flow is ²normally fed into the intermediate residence entity, such as storage tower or ²tank ²or the like, in its upper part and it is discharged from the lower part of the ²²intermediate residence entity via an outlet. The residence time is understood ²as²the time, which lapses between the entry of the fibre suspension into the ²residence²entity and the discharge of the fibre suspension from the intermediate ²residence ²entity. The residence time for intermediate residence entities which operate ²under ²continuous feed and discharge can be calculated in a manner known as such. The²<DP=6>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²6²residence time may be, for example, at least 4 h, preferably at least 5 h, ²sometimes even at least 6 h. Prolonged residence times are typically ²encountered ²during planned or unplanned process stops. According to one preferable ²embodiment the germinant surfactant or the treatment system containing it is² added to the fibre suspension when fibre suspension's residence time in the ²intermediate residence entity has exceeded 2 hours.²The addition point of the germinant surfactant may be located at the lower ²part of ²the intermediate residence entity. The term "lower part of the intermediate²residence entity" denotes here the part of the intermediate residence entity ²that is ²located under the horizontal line that divides the residence entity into two ²parts of ²equal height, draw between the bottom and the upper end of the intermediate ²residence entity. The addition point of the germinant surfactant is preferably ²²located at the mixing zone of the intermediate residence entity at the lower ²part of²the intermediate residence entity.²Alternatively, or in addition, the germinant surfactant may be added at or ²after the ²outlet of the intermediate residence entity, but before the formation of the ²fibrous ²web. Preferably the germinant surfactant is added at or after the outlet of ²the²intermediate residence entity.²According to one embodiment of the invention the time delay between the ²addition ²of the germinant surfactant and the formation of the fibrous web may be less ²than ²60 min, preferably less than 45 min, more preferably less than 30 min. ²Preferably²the time delay is at least 15 min, but it is possible that in certain ²embodiments the ²time delay may be less than 15 minutes, even less than 10 minutes. The ²intermediate residence entity may be, for example in this case, the storage ²tower ²or the last broke tower. The relatively short time delay between the addition ²of the ²germinant surfactant and the web formation makes it possible to add the²germinant surfactant close to the headbox of a paper or board machine. This ²means that for example after a production stop the germinant surfactant can be ²²added after the intermediate residence entity, and the possible detrimental²<DP=7>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²7²endospore formation in the intermediate residence entity during the stop can ²be ²alleviated.²According to one embodiment of the invention the germinant surfactant is added ²to²the fibre suspension at or after the outlet of an intermediate residence ²entity, which²is followed by one or more intermediate residence entities. For example, the ²germinant surfactant is added to the fibre suspension at or after the outlet ²of a ²pulper for pulp or broke or the outlet of the first broke tower in series of ²broke ²towers. The fibre suspension is transferred from the outlet to a following²intermediate residence entity. The residence time in the following ²intermediate²residence entities is preferably at maximum 2 hours in each. According to this ²²embodiment, when there is at least one intermediate residence entity between ²the ²addition point and the formation of the fibrous web, the time delay between ²the ²addition of the germinant surfactant and the formation of the fibrous web may ²be at²least 15 min, preferably at least 30 min, more preferably at least 45 min, ²even²more preferably at least 60 min and less than 8 hours. It is possible that at ²least ²one biocidal agent, as defined elsewhere in this context, may be added to the ²fibre ²suspension between the first and the successive intermediate residence ²entity / entities, for reducing and / or destroying the sensitised endospores.² According to one embodiment the fibre suspension is diluted from a first ²concentration, usually storage concentration, to a second concentration with ²dilution water. The fibre suspension may be diluted from high concentration of ²> 6 ²weight-%, sometimes > 10 weigh-%, to a second low concentration of < 4 weight-²%, preferably < 1 weigh-%. Often the first concentration may be in the range ²of 4 ¨²10 weight-%, quite often 6¨ 8 weight-%. The germinant surfactant may be added ²to the fibre suspension either before or after the dilution, and it is shows ²good ²effect in sensitising endospores both in high and low fibre suspension ²concentrations. According to one embodiment the germinant surfactant is added ²to²fibre suspension, which has a concentration in the range of 0.1 ¨ 6 weight-%, ²preferably 0.1 ¨ 4 weight-%, more preferably 0.1 ¨ 2 weight-%, even more ²preferably 0.1 ¨ 1.5 weight-%. It has been observed that the addition of the ²germinant surfactant to fibre suspension with a low concentration provides an²<DP=8>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²8²effective mixing of the germinant surfactant to the fibre suspension while ²producing active sensitisation of the bacterial endospores. On the other hand ²the ²addition of the germinant surfactant to fibre suspension with a high ²concentration ²provides advantages in view of process economy.² According to one embodiment the germinant surfactant is added to the fibre ²suspension together with the dilution water in order to ensure the proper ²mixing of ²the germinant surfactant throughout the fibre suspension.²According to one embodiment of the invention the amount of bacterial ²endospores, ²given as CFU / ml, in the fibre suspension is reduced at least 20 %, preferably ²at ²least 40 %, sometimes even at least 50 %, between the outlet of the ²intermediate ²residence entity and the formation of the fibrous web.²After the initial formation of the fibrous web the web is dried in a drying ²section of a ²pulp, paper, board or tissue machine. The temperature in the drying section is ²²typically at least 100 C, preferably at least 110 C, more preferably at ²least 120 ²C, and the fibrous web is preferably subjected to this temperature for at ²least 0.3 ²min, more preferably for at least 0.5 min, preferably for at least 1 min in ²the drying²section. According to one preferable embodiment the formed fibrous web is ²dried ²at a temperature of > 90 C and the sensitised bacterial endospores, such as ²germinated or partially germinated bacterial endospores, are destroyed and ²killed. ²The exposure to heat energy thus provides the final effective destruction of ²sensitised endospores. The bacterial endospore content in the dried web may be ²...² 1000 CFU / g, preferably 500 CFU / g, more preferably 250 CFU / g.²According to one embodiment of the invention at least one biocidal agent may ²be ²added to the fibre suspension, before and / or after the addition of the ²germinant ²surfactant. The at least one biocidal agent is different from germinant ²surfactant.² According to one preferable embodiment at least one biocidal agent is added ²preferably prior to addition of the germinant surfactant. It is also possible ²to add ²the germinant surfactant to the fibre suspension simultaneously but preferably ²²separately with the biocidal agent. Use of the treatment system that comprises²<DP=9>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²9²germinant surfactant and biocidal agent(s) provide advantageous effect, where ²a ²reduction both in amounts of vegetative bacteria and endospores is ²significantly ²higher than the reduction achievable by biocidal agent(s) or germinant ²surfactant ²alone.² It is possible to add one or several different biocidal agents to the fibre ²suspension, either before and / or after the addition of the germinant ²surfactant. In ²case of several different biocidal agents, it is possible to add first ²biocidal agent(s) ²before the addition of the germinant surfactant and second biocidal agent(s) ²after²the addition of the germinant surfactant. This provides great flexibility for ²the ²dosing of various biocidal agents and possibilities to obtain an optimal ²control of ²bacteria and endospores.²Biocidal agent, which may be added to the fibre suspension, preferably prior ²to the²germinant surfactant addition, may be oxidizing biocide, which is preferably ²selected from chlorine; alkali and alkaline earth hypochlorite salts; ²hypochlorous ²acid; chlorinated isocyanurates; bromine; alkali and alkaline earth ²hypobromite ²salts; hypobromous acid; bromine chloride; chlorine dioxide; ozone; hydrogen ²peroxide; peroxy compounds, such as performic acid, peracetic acid, ²percarbonate²or persulfate; halogenated hydantoins, such as monohalodimethylhydantoins; ²dihalodimethylhydantoins; perhalogenated hydantoins; monochloramines; ²monobromamines; dihaloamines; trihaloamines; urea reacted with an oxidant, the ²²oxidant being e.g. alkali and alkaline earth hypochlorite salts or alkali and ²alkaline ²earth hypobromite salts; ammonium salts, e.g. ammonium bromide or ammonium²sulphate, reacted with an oxidant, the oxidant being preferably alkali and ²alkaline ²earth hypochlorite salts or alkali and alkaline earth hypobromite salts; or ²any ²combination thereof. Alkali and alkaline earth hypochlorite salts, such as ²sodium ²hypochlorite, are being preferred as oxidizing biocide.²Alternatively the biocidal agent, which may be added to the fibre suspension, ²preferably prior to the germinant surfactant addition, may be non-oxidizing ²biocide, ²which is preferably selected from glutaraldehyde; 2,2-dibromo-3-²nitrilopropionamide (DBNPA); 2-bromo-2-nitropropane-1,3-diol (Bronopol);²<DP=10>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821² quaternary ammonium compounds (quats), such as n-alkyl dimethyl benzyl ²ammonium chloride, didecyl dimethyl ammonium chloride (DDAC) or alkenyl ²dimethyl ammonium chloride; carbamates; 5-chloro-2-methyl-4-isothiazolin-3-one ²²(CM IT); 2-methyl-4-isothiazol in-3-one (MIT); 1,2-dibromo-2,4-dicyanobutane,²5 bis(trichloromethyl)sulfone; 2-bromo-2-nitrostyrene; 4,5-dichloro-1,2-²dithioI-3-one;²2-n-octy1-4-isothiazol in-3-one; 1,2-benzisothiazol in-3-one; ortho-²phthaldehyde; ²other guanidines than dodecylguanidine salts, biguanidines, pyrithiones; 3-²iodo-²propynyl-N-butylcarbamate; phosphonium salts, such as tetrakis hydroxymethyl ²phosphonium sulfate (THPS); dazomet; 2-(thiocyanomethylthio) benzothiazole;²10 methylene bisthiocyanate (MBT); or any combination thereof.²According to one preferable embodiment it is possible to add both oxidative ²and ²non-oxidative biocides to the fibre suspension, before and / or after the ²addition of ²germinant surfactant or simultaneously with the germinant surfactant. The²treatment system comprises biocidal agent, which may be selected from ²oxidative²and non-oxidative biocide, and combinations thereof. The treatment system may ²thus comprise a plurality of different biocidal agents, which may be oxidative ²²and / or non-oxidative biocides. According to one embodiment the germinant ²surfactant and biocidal agent(s) are used sequentially, preferably by adding²biocidal agent(s) before the germinant surfactant.²Biocidal agent(s), which are used with the germinant surfactant or as a part ²of the ²treatment system may be used in dosages which are conventional in the art. In ²some embodiment it is possible to use lower dosages of biocidal agent(s) after ²the²germinant surfactant has sensitised the bacterial endospores, disrupted their²protective structures and made them more sensitive for biocidal agent(s). At ²least ²one active halogen containing biocidal agent may be added to the fibre ²suspension in amount of 1 ¨ 10 ppm, preferably 2 ¨ 8 ppm, more preferably 3 ¨ ²5 ²ppm, given as active halogen.² The temperature of the fibre suspension during the addition of the germinant ²surfactant may be at least +20 C, preferably +40 ¨ +70 C. It has been ²observed ²that the elevated temperature of the fibre suspension may improve the²<DP=11>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²11²sensitisation effect obtainable by the germinant surfactant, or at least does ²not²have any negative influence on the effect obtainable with the germinant ²surfactant.²The pH of the pulp suspension is preferably in the pH range of 4 ¨ 12 in order ²to² guarantee the optimal interaction of the germinant surfactant and vegetative ²bacteria and / or germinant surfactant and the bacterial endospores. The ²addition of ²the germinant surfactant at dosage level that provides a decrease in the ²endospore amount does not significantly change pH of the fibre suspension. The ²²pH change of the fibre suspension is less than 0.5 pH units, preferably less ²than²0.25 pH units, more preferably less than 0.1 pH units, measured after the ²addition ²of the germinant surfactant. This is advantageous because stable pH of the ²fibre ²suspension minimises the disturbance for other chemical systems used in or ²added to the fibre suspension.²The pulp suspension treated with the germinant surfactant may be formed into a ²²fibrous web of paper, board or tissue and dried. The method according to the ²present invention is especially suitable for producing a hygienic fibrous web, ²such ²as hygienic web of paper, board, tissue or the like. In the present context ²the term ²"hygienic fibrous web" encompasses fibrous webs comprising cellulosic fibres,²where bacterial endospore content in the dried web is less than about 1000 ²CFU / g, preferably less than about 500 CFU / g, more preferably less than about ²250 CFU / g. The endospore content is preferably '. 1000 CFU / g, preferably ... ²500 ²CFU / g, more preferably 250 CFU / g. According to one embodiment the hygienic ²fibrous web has a bacterial endospore content in the dried web < 100 CFU / g,² preferably < 75 CFU / g, more preferably 50 CFU / g.²The fibre suspension comprises lignocellulosic and / or cellulosic fibres, ²optional ²papermaking additives and water. The fibre suspension may comprise, ²alternatively or in addition, microfibrillated cellulose. In this context ²lignocellulosic²fibres are fibres originating from wood, for example from softwood or ²hardwood. ²The lignocellulosic / cellulosic fibres may be virgin fibres obtained by any ²known ²pulping process and / or they may be recycled fibres and / or they may originate ²from ²broke. For example, the fibre stock may comprise cellulosic fibres obtained by²<DP=12>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²12²mechanical pulping, chemical pulping, chemithermomechanical pulping or by ²repulping recycled or recovered fibres. The lignocellulosicicellulosic fibres ²can be ²refined or unrefined, bleached or unbleached. The lignocellulosic / cellulosic ²fibres ²may be recycled unbleached or bleached Kraft pulp fibres, hardwood semi-² chemical pulp fibres, grass pulp fibres or any mixtures thereof.²EXPERIMENTAL²Some embodiments of the invention are described in the following non-limiting ² examples.²Example 1²Objective of this laboratory test was to study bacterial killing and spore ²sensitisation effect of a germinant surfactant composition comprising 35 ²weight-% ² of dodecylguanidine hydrochloride (DGH) and dipropyleneglycol as solvent in ²paper machine process water, at variable pulp consistency.²Authentic circulation water, with low fibre content, and authentic broke, with ²high ²fibre content, were collected from a paper machine, which produced food ²packaging board. Circulation water and broke samples were mixed together to ²obtain 6 samples in total, at 3 different pulp consistency levels.²To obtain equal bacterial spore content in the samples at the start of the ²experiment, each sample was spiked with additional bacterial spores. Target ²spore²level in the sample was set to ca. 10 000 CFU / ml. The spore solution for ²spiking²was prepared as follows: authentic spore-forming bacteria that were isolated ²from ²a paper making process were pre-grown for 2 days at +37 C in a modified ²nutrient broth, after which the mature spores were harvested, and washed by ²using centrifugation and cold water.² Out of the 6 samples, 3 test samples were treated with germinant surfactant ²comprising dodecylguanidine hydrochloride (DGH) and 3 samples were left ²without any chemical addition as reference samples. After addition of ²germinant²<DP=13>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²13²surfactant, the test samples as well as the reference samples (no addition) ²were ²stored at 45 C, mixing of 180 rpm, for 30 minutes, followed by quantification ²of ²total aerobic bacteria (non-pasteurized samples) and aerobic spores (plate ²count ²agar, +32 C, 2 days incubation). Prior to the aerobic spore determination, ²samples²were pasteurized at +82 C for 10 min. Weight of suspended solids per litre of ²liquid, i.e. pulp consistency, was determined at the end of the test (dry ²weight of ²sample per total weight of sample). Results of are shown in Table 1.²Table 1 Results of Example 1²Pulp DGH Aerobic spores, Spore Total aerobic ²Bacterial²consistency content cfu / rnI(+82 C,10 reduction ²(') / 0) bacteria killing²(w / w-%) (mg / L as min, +32 C, 2d (+32 C, 2d ²efficacy (%)²active) PCA) PCA)²0.1 0 20 000 98 300 000 ²100² 100 400 300²3 0 5 400 87 40 000 78²100 700 9 000²6 0 5 100 45 170 000 ²55²100 2 800 77 000²Results in Table 1 show that germinant surfactant comprising DGH-biocide, at ²dosage 100 mg / I as active component, showed excellent bacterial killing (100%) ²²and spore reduction (98%) effect in low 0.1 % consistency sample. Similarly, ²good²bacterial killing (78%) and spore reduction (87%) effects were obtained in 3 w-²% ²consistency sample. In the sample having highest 6 % consistency, the ²bacterial ²killing (55%) and spore reduction efficacy (45%) of the germinant surfactant ²were ²somewhat lower than in the other samples but still significant effect could be ²²observed.² Obtained results indicate that a germinant surfactant comprising DGH may ²effectively be used to hygienise spore contaminated process streams with ²different ²pulp consistencies. It thus provides a novel tool for reduction of bacterial ²spores in ²both low and thick pulp stock, such as dilute and thick broke towers. Such a²<DP=14>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²14²hygienisation treatment, i.e. spore reduction of > 45 %, eventually helps the ²mills ²to meet strict hygiene limits set for food packaging board production.²Example 2²Authentic broke and circulation water samples were collected from an alkaline ²paper mill producing food packaging board. 1 litre of broke was stored for 2 ²days, ²+45 C, with closed cap, without mixing, in order to induce anaerobism and ²thus ²bacterial sporulation. This stagnant sample was divided to four 100 ml ²samples, ²out of which two replicate samples were treated with a germinant surfactant² comprising 35 weight-% dodecylguanidine hydrochloride (DGH) and ²dipropyleneglycol as solvent. The dosage was 70 mg / L as active DGH. Two ²replicates were left without any chemical additions as reference samples.²After chemical contact time of 5 min, all samples were diluted three times ²with the²circulation water and incubated for 30 minutes, at +45 C, mixing of 160 rpm. ²Total ²aerobes (PCA, +37 C) and aerobic spores (PGA, +37 C) were measured at start ²from reference samples and after the total contact time of 35 min from all ²samples. ²Results are shown in Figure 1.² In Figure 1:²A = fresh broke at start, no DGH²B = Stagnant 2 d old broke, no DGH²C = Stagnant 2 d old broke mixed with dilution water, no DGH²D = Stagnant 2 d old broke treated with DGH ad 70 ppm (as active) for 5 min, ²and² mixed with dilution water²Figure 1 shows for reference samples that fresh broke contained a large ²amount, ²1.6 x 107 CFU / ml, of total aerobic bacteria, but little, 14 CFU / ml, aerobic ²spores. ²After 2 days of "stagnant" storage at +45 C, the aerobic spore count of broke²markedly increased from 14 CFU / ml to 500 CFU / ml, and total aerobes level ²remained at high level, 9,3 x 106 CFU / ml. Due to addition of the dilution ²water, ²which was circulation water with 26 spores / ml, aerobic spore count decreased ²from 500 CFU / ml to 330 CFU / ml.²<DP=15>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821² When the stagnant and diluted broke was treated with germinant surfactant ²comprising DGH, at dosage of 70 mg / I active, the level of aerobic spores ²decreased from 330 CFU / ml to 120 CFU / ml, and total aerobic bacteria level²5 decreased slightly from 9 x 106 CFU / ml to 2 x 106. Obtained results thus ²indicate²that the germinant surfactant comprising DGH may be used at economically ²feasible treatment level for effective broke hygienisation, i.e. for spore ²reduction of ²> 60 %, which is a significant improvement for hygienic paper or board ²production, ²and killing of aerobic bacteria, in conditions that correspond to authentic²10 processing of broke at food packaging board mills. Germinant surfactant ²comprising DGH thus provides a unique spore control solution for hygienic ²board ²production.²Example 3²15 Objective of this laboratory test was to study effect of biocidal pre-²treatment on²bacterial killing and spore sensitisation efficacy of a germinant surfactant ²comprising 35 weight-% of dodecylguanidine hydrochloride (DGH) and ²dipropyleneglycol as solvent in paper machine process water.²Authentic circulation water (1 litre) was collected from a paper machine ²producing²food packaging board and divided into 4 samples with volume of 50 ml. To ²obtain ²equal bacterial spore content in the samples at start of the experiment, each ²sample was spiked with additional bacterial spores. The target level for ²spores ²was c.a. 10 000 CFU / ml. The spore solution for spiking was prepared as ²follows:²authentic spore-forming bacteria that were isolated from a paper making ²process ²were pre-grown for 2 days at +37 C in modified nutrient broth, after which ²the ²mature spores were harvested, and washed by using centrifugation and cold ²water. Out of the 4 samples,²- the first sample was left without any chemical addition as a reference² sample.²- the second sample was treated with sodium hypochlorite, at dosage of 5 ²mg / I, given as active chlorine;²<DP=16>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²16²- the third sample was treated with a germinant surfactant comprising ²dodecylguanidine hydrochloride (DGH), at dosage level of 100 mg / I, given ²as active compound; and²- the fourth sample was treated with sodium hypochlorite, at dosage of 5²mg / I, given as active chlorine) for 1 minute, after which the third sample was²treated with a germinant surfactant comprising dodecylguanidine ²hydrochloride (DGH), at dosage level of 100 mg / I, given as active ²compound;² Samples were stored at 45 C, under mixing of 180 rpm, for 30 minutes except ²samples 2 and 4, which were in addition pre-treated with sodium hypochlorite ²for 1 ²minute. After the treatment the amount of total aerobic bacteria (non-²pasteurized ²samples) and aerobic spores were quantified (plate count agar, +32 C, 2 days ²incubation). Prior to the aerobic spore determination, samples were ²pasteurized at²+82 C for 10 min. Results of are shown in Table 2²Table 2 Results of Example 3.²Sample Total aerobic Aerobic spores ²Redox²bacteria PCA +32,, ²PCA +32, 30min 30min (45 C ²(45 C²1. Process water, no biocides 7 000 000 13 000 ²7.6 165²2. Process water with sodium 320 000 17 000 ²7.7 154²hypochlorite as 5 ppm (as active²Chlorine)²3. Process water with DGH as 100 10 000 3 000 7.6 166²ppm (as active)²4. Process water, with sodium 4 700 900 ²7.7 147²hypochlorite as 5 ppm (as act CI)²pre-treatment (1min), followed by²DGH treatment as 100ppm (as²active)²<DP=17>²CA 03080946 2020-04-29²WO 2019 / 092317 PCT / F12018 / 050821²17²Results in Table 3 show that sodium hypochlorite showed good killing effect ²against total aerobic bacteria, whereby the level decreased from 7 000 000 ²CFU / ml to 32 000 CFU / ml, but it did not have any effect on bacterial spores, ²as the ²spore counts were at 17 000 CFU / ml level despite the chlorine treatment.²Germinant surfactant comprising DGH showed alone an excellent bacterial ²killing ²effect, as the total aerobic bacteria level decreased from 7 000 000 CFU / ml to ²² 000 CFU / ml, and also good spore sensitisation effect, as the aerobic spore ²count decreased from 13 000 to 3000 CFU / ml, i.e. spore reduction of > 70 %,²10 which is a significant improvement for hygienic paper or board production. ²The ²most effective killing and spore reduction effect was obtained with sodium ²hypochlorite as pre-treatment, followed by treatment with germinant surfactant ²²comprising DGH. This dual biocide treatment, which did not change process pH ²nor ORP, caused a drastic drop in total aerobic bacteria level from 7 000 000²CFU / ml to 4 700 CFU / ml and in bacterial spore count from 13 000 CFU / ml to 900 ²CFU / ml, i.e. spore reduction of > 90 %, which is a significant improvement in ²hygienic paper or board production. Obtained results indicate clearly that ²fast ²acting biocides, such as sodium hypochlorite, may preferably be used as a pre-²treatment before dosage of germinant surfactant comprising DGH for spore²reduction purposes. Germinant surfactant comprising DGH together with sodium ²hypochlorite pre-treatment provides a novel tool for easy and quick reduction ²of ²bacterial spores, such as spore reduction > 90 %, in pulp and paper process ²streams which eventually helps food packaging board mills to meet strict ²hygiene ²limits of final board.²Even if the invention was described with reference to what at present seems to ²be ²the most practical and preferred embodiments, it is appreciated that the ²invention ²shall not be limited to the embodiments described above, but the invention is ²intended to cover also different modifications and equivalent technical ²solutions²within the scope of the enclosed claims.²<DP=18>²18²***²In some aspects, embodiments of the present invention as described herein ²includes the following items:² 1. A method for manufacturing a fibrous web, the method comprising²(a) obtaining at least one fibre suspension of lignocellulosic and / or ²cellulosic fibres,²(b) feeding the fibre suspension into an intermediate residence entity,²(c) discharging fibre suspension, which comprises bacterial endospores, out of ²the ²intermediate residence entity via an outlet after a residence time of at least ²2 hours²in the intermediate residence entity,²(d) forming after a time delay the fibre suspension into a fibrous web,²wherein²bacterial endospores are sensitised by adding a germinant surfactant, which²comprises a primary or secondary ammonium head group and a linear ²unsubstituted²C12-alkyl tail, to the fibre suspension at an addition point, which is located ²at the²lower part of the intermediate residence entity or after the outlet of the ²intermediate ²residence entity, but before the formation of the fibrous web.²2. The method according to item 1, wherein the fibrous web is a web of paper, ²board²or tissue.²3. The method according to item 1 or 2, wherein the intermediate residence ²entity ²is a pulper, a storage tower or a broke tower.²4. The method according to any one of items 1 to 3, wherein in diluting the ²fibre²suspension from a first concentration to a second concentration with dilution ²water, ²whereby the germinant surfactant is added to the fibre suspension together ²with the ²dilution water.²5. The method according to any one of items 1 to 4, wherein the germinant ²surfactant is selected from the group consisting of: n-dodecylamine, n-²dodecylguanidine, dodecylamine salt, dodecylguanidine salt, and any of their ²mixture.²Date recue / Date received 2024-01-23²<DP=19>²19²6. The method according to item 5, wherein the dodecylguanidine salt is ²dodecylguanidine hydrochloride.²7. The method according to any one of items 1 to 6, wherein the time delay ²between²the addition of the germinant surfactant and the formation of the fibrous web ²is less ²than 60 min.²8. The method according to any one of items 1 to 7, wherein the time delay ²between²the addition of the germinant surfactant and the formation of the fibrous web ²is less²than 45 min.²9. The method according to any one of items 1 to 8, wherein the time delay ²between ²the addition of the germinant surfactant and the formation of the fibrous web ²is less² than 30 min.²10. The method according to any one of items 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 15 min and less than 8 hours, when there is at least one ²intermediate²residence entity between the addition point and the fibrous web formation.²11. The method according to any one of items 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 30 min, and less than 8 hours, when there is at least one ²intermediate²residence entity between the addition point and the fibrous web formation.²12. The method according to any one of items 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 45 min, and less than 8 hours, when there is at least one ²intermediate²residence entity between the addition point and the fibrous web formation.²13. The method according to any one of items 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous²Date recue / Date received 2024-01-23²<DP=20>²20²web is at least 60 min, and less than 8 hours, when there is at least one ²intermediate²residence entity between the addition point and the fibrous web formation.²14. The method according to any one of items 1 to 13, wherein the germinant² surfactant is added in an amount of > 30 ppm, and given as active surfactant.²15. The method according to any one of items 1 to 14, wherein the germinant ²surfactant is added in the amount of 60 ¨ 200 ppm, and given as active ²surfactant.²16. The method according to any one of items 1 to 15, wherein the germinant ²surfactant is added in the amount of 70 ¨ 100 ppm, and given as active ²surfactant.²17. The method according to any one of items 1 to 16, wherein drying the ²formed ²fibrous web at a temperature of > 90 C and destroying the sensitised ²bacterial ²endospores.²18. The method according to item 17, wherein the bacterial endospore content ²in ²the dried web is 5. 1000 CFU / g.²19. The method according to item 17 or 18, wherein the bacterial endospore ²content²in the dried web is .5 500 CFU / g.²20. The method according to any one of items 17 to 19, wherein the bacterial²endospore content in the dried web is 5 250 CFU / g.²21. The method according to any one of items 1 to 20, wherein the amount of ²bacterial endospores, given as CFU / ml, in the fibre suspension is reduced at ²least ²20 % between the outlet of the intermediate residence entity and the formation ²of ²the fibrous web.²22. The method according to any one of items 1 to 21, wherein the amount of ²bacterial endospores, given as CFU / ml, in the fibre suspension is reduced at ²least²Date recue / Date received 2024-01-23²<DP=21>²21²40 % between the outlet of the intermediate residence entity and the formation ²of ²the fibrous web.²23. The method according to any one of items 1 to 22, wherein at least one ²biocidal² agent is added to the fibre suspension.²24. The method according to item 23, wherein at least one biocidal agent is ²added ²to the fibre suspension prior to addition of the germinant surfactant.²25. The method according to item 23 or 24, wherein at least one biocidal agent ²is²an oxidizing biocide.²26. The method according to item 25, wherein the oxidizing biocide is selected ²from ²the group consisting of chlorine; alkali and alkaline earth hypochlorite ²salts;²hypochlorous acid; chlorinated isocyanurates; bromine; alkali and alkaline ²earth²hypobromite salts; hypobromous acid; bromine chloride; chlorine dioxide; ²ozone; ²hydrogen peroxide; peroxy compounds; halogenated hydantoins; perhalogenated ²hydantoins; monochloramines; monobromamines; dihaloamines; trihaloamines; ²urea reacted with an oxidant; ammonium salts reacted with an oxidant; and any²combination thereof.²27. The method according to item 26, wherein the peroxy compounds are selected ²²from the group consisting of performic acid, peracetic acid, percarbonate, ²persulfate ²and a combination thereof.²28. The method according to item 26, wherein the halogenated hydantoins are ²selected from the group consisting of monohalodimethylhydantoins, ²dihalodimethyl-²hydantoins and a combination thereof.²29. The method according to item 26, wherein the oxidant reacted with urea is ²selected from alkali and alkaline earth hypochlorite salts; alkali and ²alkaline earth ²hypobromite salts; and a combination thereof.²Date recue / Date received 2024-01-23²<DP=22>²22²30. The method according to item 26, wherein the ammonium salts are selected²from ammonium bromide, ammonium sulfate and a combination thereof.²31. The method according to item 26, wherein the oxidant reacted with the²ammonium salt is selected from alkali and alkaline earth hypochlorite salts; ²alkali ²and alkaline earth hypobromite salts; and a combination thereof.²32. The method according to item 23 or 24, wherein at least one biocidal agent ²is a²non-oxidizing biocide.²33. The method according to item 32, wherein the non-oxidizing biocide is ²selected ²from the group consisting of glutaraldehyde; 2,2-dibromo-3-nitrilopropionamide ²²(DBNPA); 2-bromo-2-nitropropane-1,3-diol (Bronopol); quaternary ammonium ²compounds (quats); carbamates; 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT); ²2-²methyl-4-isothiazolin-3-one (MIT); 1,2-²dibromo-2,4-dicyanobutane,²bis(trichloromethyl)sulfone; 2-bromo-2-nitrostyrene; 4,5-dichloro-1,2-dithio1-²3-one; ²2-n-octy1-4-isothiazolin-3-one; 1,2-benzisothiazolin-3-one; ortho-²phthaldehyde; ²other guanidines than dodecylguanidine salts, biguanidines, pyrithiones; 3-²iodo-²propynyl-N-butylcarbamate; phosphonium salts; dazomet; 2-(thiocyanomethylthio)² benzothiazole; methylene bisthiocyanate (MBT); and any combination thereof.²34. The method according to item 33, wherein the quaternary ammonium ²compounds (quats) are selected from the group consisting of n-alkyl dimethyl ²benzyl ²ammonium chloride, didecyl dimethyl ammonium chloride (DDAC), alkenyl dimethyl²ammonium chloride, and a combination thereof.²35. The method according to item 33, wherein the phosphonium salt is tetrakis ²hydroxymethyl phosphonium sulfate (THPS).²36. The method according to any one of items 1 to 35, wherein at least one ²active ²halogen containing biocidal agent is added to the fibre suspension in amount ²of 1 ¨ ²10 ppm, given as active halogen.²Date recue / Date received 2024-01-23²<DP=23>²23²37. The method according to any one of items 23 to 36, wherein the germinant ²surfactant and biocidal agent(s) are used sequentially.²Date recue / Date received 2024-01-23²

Claims

<DP=1>²24²CLAIMS²1. A method for manufacturing a fibrous web, the method comprising²(a) obtaining at least one fibre suspension of lignocellulosic and / or ²cellulosic fibres,² (b) feeding the fibre suspension into an intermediate residence entity,²(c) discharging fibre suspension, which comprises bacterial endospores, out of ²the ²intermediate residence entity via an outlet after a residence time of at least ²2 hours ²in the intermediate residence entity,²(d) forming after a time delay the fibre suspension into a fibrous web,²wherein²bacterial endospores are sensitised by adding a germinant surfactant, which ²comprises a primary or secondary ammonium head group and a linear ²unsubstituted ²C12-alkyl tail, to the fibre suspension at an addition point, which is located ²at the ²lower part of the intermediate residence entity or after the outlet of the ²intermediate²residence entity, but before the formation of the fibrous web.²2. The method according to claim 1, wherein the fibrous web is a web of paper, ²²board or tissue.²3. The method according to claim 1 or 2, wherein the intermediate residence ²entity²is a pulper, a storage tower or a broke tower.²4. The method according to any one of claims 1 to 3, wherein in diluting the ²fibre ²suspension from a first concentration to a second concentration with dilution ²water,²whereby the germinant surfactant is added to the fibre suspension together ²with the²dilution water.²5. The method according to any one of claims 1 to 4, wherein the germinant ²surfactant is selected from the group consisting of: n-dodecylamine, n-²dodecylguanidine, dodecylamine salt, dodecylguanidine salt, and any of their²mixture.²Date recue / Date received 2024-01-23²<DP=2>²25²6. The method according to claim 5, wherein the dodecylguanidine salt is ²dodecylguanidine hydrochloride.²7. The method according to any one of claims 1 to 6, wherein the time delay ²between²the addition of the germinant surfactant and the formation of the fibrous web ²is less²than 60 min.²8. The method according to any one of claims 1 to 7, wherein the time delay ²between ²the addition of the germinant surfactant and the formation of the fibrous web ²is less² than 45 min.²9. The method according to any one of claims 1 to 8, wherein the time delay ²between ²the addition of the germinant surfactant and the formation of the fibrous web ²is less ²than 30 min.²10. The method according to any one of claims 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 15 min and less than 8 hours, when there is at least one ²intemiediate ²residence entity between the addition point and the fibrous web formation.²11. The method according to any one of claims 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 30 min, and less than 8 hours, when there is at least one ²intermediate ²residence entity between the addition point and the fibrous web formation.²12. The method according to any one of claims 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous ²web is at least 45 min, and less than 8 hours, when there is at least one ²intemiediate ²residence entity between the addition point and the fibrous web formation.²13. The method according to any one of claims 1 to 6, wherein the time delay ²between the addition of the germinant surfactant and the formation of the ²fibrous²Date recue / Date received 2024-01-23²<DP=3>²26²web is at least 60 min, and less than 8 hours, when there is at least one ²intermediate²residence entity between the addition point and the fibrous web formation.²14. The method according to any one of claims 1 to 13, wherein the germinant² surfactant is added in an amount of > 30 ppm, and given as active surfactant.²15. The method according to any one of claims 1 to 14, wherein the germinant ²surfactant is added in the amount of 60 ¨ 200 ppm, and given as active ²surfactant.²16. The method according to any one of claims 1 to 15, wherein the germinant²surfactant is added in the amount of 70 ¨ 100 ppm, and given as active ²surfactant.²17. The method according to any one of claims 1 to 16, wherein drying the ²formed ²fibrous web at a temperature of > 90 C and destroying the sensitised ²bacterial ²endospores.²18. The method according to claim 17, wherein the bacterial endospore content ²in ²the dried web is 5. 1000 CFU / g.²19. The method according to claim 17 or 18, wherein the bacterial endospore ²content in the dried web is 5 500 CFU / g.²20. The method according to any one of claims 17 to 19, wherein the bacterial²endospore content in the dried web is 5 250 CFU / g.²21. The method according to any one of claims 1 to 20, wherein the amount of ²bacterial endospores, given as CFU / ml, in the fibre suspension is reduced at ²least ²20 % between the outlet of the intermediate residence entity and the formation ²of ²the fibrous web.²22. The method according to any one of claims 1 to 21, wherein the amount of ²bacterial endospores, given as CFU / ml, in the fibre suspension is reduced at ²least²Date recue / Date received 2024-01-23²<DP=4>²27²40 % between the outlet of the intermediate residence entity and the formation ²of ²the fibrous web.²23. The method according to any one of claims 1 to 22, wherein at least one ²biocidal² agent is added to the fibre suspension.²24. The method according to claim 23, wherein at least one biocidal agent is ²added ²to the fibre suspension prior to addition of the germinant surfactant.²25. The method according to claim 23 or 24, wherein at least one biocidal ²agent is²an oxidizing biocide.²26. The method according to claim 25, wherein the oxidizing biocide is ²selected from ²the group consisting of chlorine; alkali and alkaline earth hypochlorite ²salts;²hypochlorous acid; chlorinated isocyanurates; bromine; alkali and alkaline ²earth²hypobromite salts; hypobromous acid; bromine chloride; chlorine dioxide; ²ozone; ²hydrogen peroxide; peroxy compounds; halogenated hydantoins; perhalogenated ²hydantoins; monochloramines; monobromamines; dihaloamines; trihaloamines; ²urea reacted with an oxidant; ammonium salts reacted with an oxidant; and any²combination thereof.²27. The method according to claim 26, wherein the peroxy compounds are ²selected ²from the group consisting of performic acid, peracetic acid, percarbonate, ²persulfate ²and a combination thereof.²28. The method according to claim 26, wherein the halogenated hydantoins are ²selected from the group consisting of monohalodimethylhydantoins, ²dihalodimethyl-²hydantoins and a combination thereof.²29. The method according to claim 26, wherein the oxidant reacted with urea is ²²selected from alkali and alkaline earth hypochlorite salts; alkali and ²alkaline earth ²hypobromite salts; and a combination thereof.²Date recue / Date received 2024-01-23²<DP=5>²28²30. The method according to claim 26, wherein the ammonium salts are selected²from ammonium bromide, ammonium sulfate and a combination thereof.²31. The method according to claim 26, wherein the oxidant reacted with the²ammonium salt is selected from alkali and alkaline earth hypochlorite salts; ²alkali ²and alkaline earth hypobromite salts; and a combination thereof.²32. The method according to claim 23 or 24, wherein at least one biocidal ²agent is²a non-oxidizing biocide.²33. The method according to claim 32, wherein the non-oxidizing biocide is ²selected ²from the group consisting of glutaraldehyde; 2,2-dibromo-3-nitrilopropionamide ²²(DBNPA); 2-bromo-2-nitropropane-1,3-diol (Bronopol); quaternary ammonium ²compounds (quats); carbamates; 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT); ²2-²methyl-4-isothiazolin-3-one (MIT); 1,2-²dibromo-2,4-dicyanobutane,²bis(trichloromethyl)sulfone; 2-bromo-2-nitrostyrene; 4,5-dichloro-1,2-dithiol-²3-one; ²2-n-octyl-4-isothiazolin-3-one; 1,2-benzisothiazolin-3-one; ortho-²phthaldehyde; ²other guanidines than dodecylguanidine salts, biguanidines, pyrithiones; 3-²iodo-²propynyl-N-butylcarbamate; phosphonium salts; dazomet; 2-(thiocyanomethylthio)² benzothiazole; methylene bisthiocyanate (MBT); and any combination thereof.²34. The method according to claim 33, wherein the quaternary ammonium ²compounds (quats) are selected from the group consisting of n-alkyl dimethyl ²benzyl ²ammonium chloride, didecyl dimethyl ammonium chloride (DDAC), alkenyl dimethyl²ammonium chloride, and a combination thereof.²35. The method according to claim 33, wherein the phosphonium salt is tetrakis ²²hydroxymethyl phosphonium sulfate (THPS).²36. The method according to any one of claims 1 to 35, wherein at least one ²active ²halogen containing biocidal agent is added to the fibre suspension in amount ²of 1 ¨ ²10 ppm, given as active halogen.²Date recue / Date received 2024-01-23²<DP=6>²29²37. The method according to any one of claims 23 to 36, wherein the germinant ²surfactant and biocidal agent(s) are used sequentially.²Date recue / Date received 2024-01-23²